Unravelling purinergic regulation in the epididymis: activation of V-ATPase-dependent acidification by luminal ATP and adenosine

Metastasis-associated protein 1 participates in regulating luminal acidification of the epididymis via repressing estrogen receptor alpha transcription

BACKGROUND

As a component of the nucleosome remodeling and deacetylating (NuRD) complex, metastasis-associated protein 1 (MTA1) has been reported to be abundant in male reproductive system and might participate in spermatogenesis and sperm maturation, whereas the precise functional role of MTA1 in these processes is still undetermined.

OBJECTIVE

To investigate the effect and potential function of MTA1 in male fertility.

MATERIALS AND METHODS

Mta1 knockout mice (Mta1-/- ) were employed to detect their reproductive phenotype. The pH value of Mta1-/- epididymal luminal fluid was measured, and the potential mechanism of MTA1 involved in regulating luminal acidification was detected in vivo and in vitro. A vasectomy model with abnormal pH of epididymal lumen was established to further detect the effect of MTA1 on epididymal luminal microenvironment.

RESULTS

Mta1-/- mice were fertile without any detectable defects in spermatogenesis or sperm motility while the deficiency of MTA1 could acidify the initial segment of epididymis to a certain extent. MTA1 could interact with estrogen receptor alpha (ERα) and inhibit the transcription of ERα target gene, hydrogen exchanger 3 (NHE3), and ultimately affect the epididymal luminal milieu. After vasectomy, the Mta1-/- mice presented a more acidic epididymal lumen which was closer to the normal state compared to the wild-type model.

DISCUSSION AND CONCLUSION

MTA1 is dispensable for male fertility in mice, but plays a potentially important function in regulating luminal acidification of the epididymis.

Characterization of the human fetal gonad and reproductive tract by single-cell transcriptomics

During human fetal development, sex differentiation occurs not only in the gonads but also in the adjacent developing reproductive tract. However, while the cellular composition of male and female human fetal gonads is well described, that of the adjacent developing reproductive tract remains poorly characterized. Here, we performed single-cell transcriptomics on male and female human fetal gonads together with the adjacent developing reproductive tract from first and second trimesters, highlighting the morphological and molecular changes during sex differentiation. We validated different cell populations of the developing reproductive tract and gonads and compared the molecular signatures between the first and second trimesters, as well as between sexes, to identify conserved and sex-specific features. Together, our study provides insights into human fetal sex-specific gonadogenesis and development of the reproductive tract beyond the gonads.

The multifaceted role of extracellular ATP in sperm function: From spermatogenesis to fertilization

Extracellular adenosine 5'-triphosphate (ATP) is a vital signaling molecule involved in various physiological processes within the body. In recent years, studies have revealed its significant role in male reproduction, particularly in sperm function. This review explores the multifaceted role of extracellular ATP in sperm function, from spermatogenesis to fertilization. We discuss the impact of extracellular ATP on spermatogenesis, sperm maturation and sperm-egg fusion, highlighting the complex regulatory mechanisms and potential clinical applications in the context of male infertility. By examining the latest research, we emphasize the crucial role of extracellular ATP in sperm function and propose future research directions to further.

Immunoregulatory mechanisms between epithelial clear cells and mononuclear phagocytes in the epididymis

INTRODUCTION

One of the most intriguing aspects of male reproductive physiology is the ability of the epididymis to prevent the mounting of immune responses against the onslaught of foreign antigens carried by spermatozoa while initiating very efficient immune responses versus stressors. Epithelial clear cells are strategically positioned to work in a concerted manner with region-specific heterogeneous subsets of mononuclear phagocytes to survey the epididymal barrier and regulate the balance between inflammation and immune tolerance in the post-testicular environment.

OBJECTIVE

This review aims to describe how clear cells communicate with mononuclear phagocytes to contribute to the unique immune environment in which sperm mature and are stored in the epididymis.

MATERIALS/METHODS

A comprehensive systematic review was performed. PubMed was searched for articles specific to clear cells, mononuclear phagocytes, and epididymis. Articles that did not specifically address the target material were excluded.

RESULTS

In this review, we discuss the unexpected roles of clear cells, including the transfer of new proteins to spermatozoa via extracellular vesicles and nanotubes as they transit along the epididymal tubule; and we summarize the immune phenotype, morphology, and antigen capturing, processing, and presenting abilities of mononuclear phagocytes. Moreover, we present the current knowledge of immunoregulatory mechanisms by which clear cells and mononuclear phagocytes may contribute to the immune-privileged environment optimal for sperm maturation and storage.

DISCUSSION AND CONCLUSION

Notably, we provide an in-depth characterization of clear cell-mononuclear phagocyte communication networks in the steady-state epididymis and in the presence of injury. This review highlights crucial concepts of mucosal immunology and cellcell interactions, all of which are critical but understudied facets of human male reproductive health.

Intra and intercellular signals governing sperm maturation

After their production in the testis, spermatozoa do not have the capacity to move progressively and are unable to fertilise an oocyte. They sequentially acquire these abilities following their maturation in the epididymis and their capacitation/hyperactivation in the female reproductive system. As gene transcription is silenced in spermatozoa, extracellular factors released from the epididymal epithelium and from secretory glands allow spermatozoa to acquire bioactive molecules and to undergo intrinsic modifications. These modifications include epigenetic changes and post-translational modifications of endogenous proteins, which are important processes in sperm maturation. This article emphasises the roles played by extracellular factors secreted by the epididymis and accessory glands in the control of sperm intercellular signallings and fertilising abilities.

Pump proton inhibitors display anti-tumour potential in glioma

OBJECTIVES

Glioma is one of the most aggressive brain tumours with poor overall survival despite advanced technology in surgical resection, chemotherapy and radiation. Progression and recurrence are the hinge causes of low survival. Our aim is to explain the concrete mechanism in the proliferation and progression of tumours based on tumour microenvironment (TME). The main purpose is to illustrate the mechanism of proton pump inhibitors (PPIs) in affecting acidity, hypoxia, oxidative stress, inflammatory response and autophagy based on the TME to induce apoptosis and enhance the sensitivity of chemoradiotherapy.

FINDINGS

TME is the main medium for tumour growth and progression. Acidity, hypoxia, inflammatory response, autophagy, angiogenesis and so on are the main causes of tumour progress. PPIs, as a common clinical drug to inhibit gastric acid secretion, have the advantages of fast onset, long action time and small adverse reactions. Nowadays, several kinds of literature highlight the potential of PPIs in inhibiting tumour progression. However, long-term use of PPIs alone also has obvious side effects. Therefore, till now, how to apply PPIs to promote the effect of radio-chemotherapy and find the concrete dose and concentration of combined use are novel challenges.

CONCLUSIONS

PPIs display the potential in enhancing the sensitivity of chemoradiotherapy to defend against glioma based on TME. In the clinic, it is also necessary to explore specific concentrations and dosages in synthetic applications.

Sperm acquire epididymis-derived proteins through epididymosomes

STUDY QUESTION

Are epididymosomes implicated in protein transfer from the epididymis to spermatozoa?

SUMMARY ANSWER

We characterized the contribution of epididymal secretions to the sperm proteome and demonstrated that sperm acquire epididymal proteins through epididymosomes.

WHAT IS KNOWN ALREADY

Testicular sperm are immature cells unable to fertilize an oocyte. After leaving the testis, sperm transit along the epididymis to acquire motility and fertilizing abilities. It is well known that marked changes in the sperm proteome profile occur during epididymal maturation. Since the sperm is a transcriptional and translational inert cell, previous studies have shown that sperm incorporate proteins, RNA and lipids from extracellular vesicles (EVs), released by epithelial cells lining the male reproductive tract.

STUDY DESIGN, SIZE, DURATION

We examined the contribution of the epididymis to the post-testicular maturation of spermatozoa, via the production of EVs named epididymosomes, released by epididymal epithelial cells. An integrative analysis using both human and mouse data was performed to identify sperm proteins with a potential epididymis-derived origin. Testes and epididymides from adult humans (n = 9) and adult mice (n = 3) were used to experimentally validate the tissue localization of four selected proteins using high-resolution confocal microscopy. Mouse epididymal sperm were co-incubated with carboxyfluorescein succinimidyl ester (CFSE)-labeled epididymosomes (n = 4 mice), and visualized using high-resolution confocal microscopy.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Adult (12-week-old) C57BL/CBAF1 wild-type male mice and adult humans were used for validation purposes. Testes and epididymides from both mice and humans were obtained and processed for immunofluorescence. Mouse epididymal sperm and mouse epididymosomes were obtained from the epididymal cauda segment. Fluorescent epididymosomes were obtained after labeling the epididymal vesicles with CFSE dye followed by epididymosome isolation using a density cushion. Immunofluorescence was performed following co-incubation of sperm with epididymosomes in vitro. High-resolution confocal microscopy and 3D image reconstruction were used to visualize protein localization and sperm-epididymosomes interactions.

MAIN RESULTS AND THE ROLE OF CHANCE

Through in silico analysis, we first identified 25 sperm proteins with a putative epididymal origin that were conserved in both human and mouse spermatozoa. From those, the epididymal origin of four sperm proteins (SLC27A2, EDDM3B, KRT19 and WFDC8) was validated by high-resolution confocal microscopy. SLC27A2, EDDM3B, KRT19 and WFDC8 were all detected in epithelial cells lining the human and mouse epididymis, and absent from human and mouse seminiferous tubules. We found region-specific expression patterns of these proteins throughout the mouse epididymides. In addition, while EDDM3B, KRT19 and WFDC8 were detected in both epididymal principal and clear cells (CCs), SLC27A2 was exclusively expressed in CCs. Finally, we showed that CFSE-fluorescently labeled epididymosomes interact with sperm in vitro and about 12-36% of the epididymosomes contain the targeted sperm proteins with an epididymal origin.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The human and mouse sample size was limited and our results were descriptive. The analyses of epididymal sperm and epididymosomes were solely performed in the mouse model due to the difficulties in obtaining epididymal luminal fluid human samples. Alternatively, human ejaculated sperm and seminal EVs could not be used because ejaculated sperm have already contacted with the fluids secreted by the male accessory sex glands, and seminal EVs contain other EVs in addition to epididymosomes, such as the abundant prostate-derived EVs.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that epididymosomes are capable of providing spermatozoa with a new set of epididymis-derived proteins that could modulate the sperm proteome and, subsequently, participate in the post-testicular maturation of sperm cells. Additionally, our data provide further evidence of the novel role of epididymal CCs in epididymosome production. Identifying mechanisms by which sperm mature to acquire their fertilization potential would, ultimately, lead to a better understanding of male reproductive health and may help to identify potential therapeutic strategies to improve male infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Spanish Ministry of Economy and Competitiveness (Ministerio de Economía y Competividad; fondos FEDER 'una manera de hacer Europa' PI13/00699 and PI16/00346 to R.O.; and Sara Borrell Postdoctoral Fellowship, Acción Estratégica en Salud, CD17/00109 to J.C.), by National Institutes of Health (grants HD040793 and HD069623 to S.B., grant HD104672-01 to M.A.B.), by the Spanish Ministry of Education, Culture and Sports (Ministerio de Educación, Cultura y Deporte para la Formación de Profesorado Universitario, FPU15/02306 to F.B.), by a Lalor Foundation Fellowship (to F.B. and M.A.B.), by the Government of Catalonia (Generalitat de Catalunya, pla estratègic de recerca i innovació en salut, PERIS 2016-2020, SLT002/16/00337 to M.J.), by Fundació Universitària Agustí Pedro i Pons (to F.B.), and by the American Society for Biochemistry and Molecular Biology (PROLAB Award from ASBMB/IUBMB/PABMB to F.B.). Confocal microscopy and transmission electron microscopy was performed in the Microscopy Core facility of the Massachusetts General Hospital (MGH) Center for Systems Biology/Program in Membrane Biology which receives support from Boston Area Diabetes and Endocrinology Research Center (BADERC) award DK57521 and Center for the Study of Inflammatory Bowel Disease grant DK43351. The Zeiss LSM800 microscope was acquired using an NIH Shared Instrumentation Grant S10-OD-021577-01. The authors have no conflicts of interest to declare.

Calcium Homeostasis in the Epididymal Microenvironment: Is Extracellular Calcium a Cofactor for Matrix Gla Protein-Dependent Scavenging Regulated by Vitamins

In the male reproductive tract, the epididymis is an essential organ for sperm maturation, in which sperm cells acquire mobility and the ability to fertilize oocytes while being stored in a protective microenvironment. Epididymal function involves a specialized luminal microenvironment established by the epithelial cells of epididymal mucosa. Low-calcium concentration is a unique feature of this epididymal luminal microenvironment, its relevance and regulation are, however, incompletely understood. In the rat epididymis, the vitamin D-related calcium-dependent TRPV6-TMEM16A channel-coupler has been shown to be involved in fluid transport, and, in a spatially complementary manner, vitamin K2-related γ-glutamyl carboxylase (GGCX)-dependent carboxylation of matrix Gla protein (MGP) plays an essential role in promoting calcium-dependent protein aggregation. An SNP in the human GGCX gene has been associated with asthenozoospermia. In addition, bioinformatic analysis also suggests the involvement of a vitamin B6-axis in calcium-dependent MGP-mediated protein aggregation. These findings suggest that vitamins interact with calcium homeostasis in the epididymis to ensure proper sperm maturation and male fertility. This review article discusses the regulation mechanisms of calcium homeostasis in the epididymis, and the potential role of vitamin interactions on epididymal calcium homeostasis, especially the role of matrix calcium in the epididymal lumen as a cofactor for the carboxylated MGP-mediated scavenging function.

Polarized epithelium-sperm co-culture system reveals stimulatory factors for the secretion of mouse epididymal quiescin sulfhydryl oxidase 1

Spermatozoa acquire fertilization ability through post-translational modifications. These membrane surface alterations occur in various segments of the epididymis. Quiescin sulfhydryl oxidases, which catalyze thiol-oxidation reactions, are involved in disulfide bond formation, which is essential for sperm maturation, upon transition and migration in the epididymis. Using castration and azoospermia transgenic mouse models, in the present study, we showed that quiescin sulfhydryl oxidase 1 (QSOX1) protein expression and secretion are positively correlated with the presence of testosterone and sperm cells. A two-dimensional in vitro epithelium-sperm co-culture system provided further evidence in support of the notion that both testosterone and its dominant metabolite, 5α-dihydrotestosterone, promote epididymal QSOX1 secretion. We also demonstrated that immature caput spermatozoa, but not mature cauda sperm cells, exhibited great potential to stimulate QSOX1 secretion in vitro, suggesting that sperm maturation is a key regulatory factor for mouse epididymal QSOX1 secretion. Proteomic analysis identified 582 secretory proteins from the co-culture supernatant, of which 258 were sperm-specific and 154 were of epididymal epithelium-origin. Gene Ontology analysis indicated that these secreted proteins exhibit functions known to facilitate sperm membrane organization, cellular activity, and sperm-egg recognition. Taken together, our data demonstrated that testosterone and sperm maturation status are key regulators of mouse epididymal QSOX1 protein expression and secretion.

Purinergic signaling in the male reproductive tract

Purinergic receptors are ubiquitously expressed throughout the body and they participate in the autocrine and paracrine regulation of cell function during normal physiological and pathophysiological conditions. Extracellular nucleotides activate several types of plasma membrane purinergic receptors that form three distinct families: P1 receptors are activated by adenosine, P2X receptors are activated by ATP, and P2Y receptors are activated by nucleotides including ATP, ADP, UTP, UDP, and UDP-glucose. These specific pharmacological fingerprints and the distinct intracellular signaling pathways they trigger govern a large variety of cellular responses in an organ-specific manner. As such, purinergic signaling regulates several physiological cell functions, including cell proliferation, differentiation and death, smooth muscle contraction, vasodilatation, and transepithelial transport of water, solute, and protons, as well as pathological pathways such as inflammation. While purinergic signaling was first discovered more than 90 years ago, we are just starting to understand how deleterious signals mediated through purinergic receptors may be involved in male infertility. A large fraction of male infertility remains unexplained illustrating our poor understanding of male reproductive health. Purinergic signaling plays a variety of physiological and pathophysiological roles in the male reproductive system, but our knowledge in this context remains limited. This review focuses on the distribution of purinergic receptors in the testis, epididymis, and vas deferens, and their role in the establishment and maintenance of male fertility.

Epididymal epithelial degeneration and lipid metabolism impairment account for male infertility in occludin knockout mice

Occludin (OCLN) is a tight junction protein and Ocln deletion mutation causes male infertility in mice. However, the role of OCLN in male reproductive system remains unknown. In this study, we used an interdisciplinary approach to elucidate the underlying mechanism of male infertility in related to OCLN function, including Ocln knockout mice as well as a combined omics analysis and immunofluorescent labelling. Our results showed that the epididymis of Ocln-null mice displayed a phenomenon resembling epididymal sperm granuloma, which occurred especially in the junctional region between caput and corpus epididymidis. Sperm motility and fertilisation capacity were also impaired in these Ocln-null mice, accompanied by enlarged tubules in the proximal regions and degeneration in the distal regions of epididymis. Cellular localization analysis showed that OCLN immunofluorescence was enriched only in the apical junction of epithelial principal cells in the proximal regions of epididymis. Integrative omics analysis revealed the downregulation of gene clusters enriched in acid secretion and fatty acid metabolism in the Ocln-null epididymis, especially the enzymes related to the unsaturated arachidonic acid pathway. The number of proton-pump V-ATPase-expression clear cells, a key player of luminal acidification in the epididymis, declined drastically from prepubertal age before sperm arrival but not in the early postnatal age. This was accompanied by programmed cell death of clear cells and increased pH in the epididymal fluid of OCLN-deficient mice. The lipidomics results showed significantly increased levels of specific DAGs conjugated to unsaturated fatty acids in the Ocln-mutant. Immunofluorescent labelling showed that the arachidonic acid converting enzyme PTGDS and phospholipase PLA2g12a were prominently altered in the principal cells and luminal contents of the Ocln-mutant epididymis. Whereas the carboxylate ester lipase CES1, originally enriched in the WT basal cells, was found upregulated in the Ocln-mutant principal cells. Overall, this study demonstrates that OCLN is essential for maintaining caput-to-corpus epithelial integrity, survival of acid-secreting clear cells, and unsaturated fatty acid catabolism in the mouse epididymis, thereby ensuring sperm maturation and male fertility.

Contribution of epididymal epithelial cell functions to sperm epigenetic changes and the health of progeny

BACKGROUND

Spermatozoa acquire their motility and fertilizing abilities during their maturation through the epididymis. This process is controlled by epididymal epithelial cells that possess features adapted to sense and respond to their surrounding environment and to communicate with spermatozoa. During the past decade, new intercellular communication processes have been discovered, including the secretion and transport of molecules from the epithelium to spermatozoa via extracellular vesicles (EVs), as well as sensing of the intraluminal milieu by cellular extensions.

OBJECTIVE AND RATIONALE

This review addresses recent findings regarding epididymal epithelial cell features and interactions between spermatozoa and the epididymal epithelium as well as epigenetic modifications undergone by spermatozoa during transit through the epididymal microenvironment.

SEARCH METHODS

A systematic search was conducted in Pubmed with the keyword 'epididymis'. Results were filtered on original research articles published from 2009 to 2021 and written in the English language. One hundred fifteen original articles presenting recent advancements on the epididymis contribution to sperm maturation were selected. Some additional papers cited in the primary reference were also included. A special focus was given to higher mammalian species, particularly rodents, bovines and humans, that are the most studied in this field.

OUTCOMES

This review provides novel insights into the contribution of epididymal epithelium and EVs to post-testicular sperm maturation. First, new immune cell populations have been described in the epididymis, where they are proposed to play a role in protecting the environment surrounding sperm against infections or autoimmune responses. Second, novel epididymal cell extensions, including dendrites, axopodia and primary cilia, have been identified as sensors of the environment surrounding sperm. Third, new functions have been outlined for epididymal EVs, which modify the sperm epigenetic profile and participate in transgenerational epigenetic inheritance of paternal traits.

WIDER IMPLICATIONS

Although the majority of these findings result from studies in rodents, this fundamental research will ultimately improve our knowledge of human reproductive physiopathologies. Recent discoveries linking sperm epigenetic modifications with paternal environmental exposure and progeny outcome further stress the importance of advancing fundamental research on the epididymis. From this, new therapeutic options for infertile couples and better counseling strategies may arise to increase positive health outcomes in children conceived either naturally or with ART.

Region-specific transcriptomic and functional signatures of mononuclear phagocytes in the epididymis

In the epididymis, prevention of autoimmune responses against spermatozoa and simultaneous protection against pathogens is important for male fertility. We have previously shown that mononuclear phagocytes (MPs) are located either in the epididymal interstitium or in close proximity to the epithelium. In the initial segments (IS), these 'intraepithelial' MPs extend slender luminal-reaching projections between epithelial cells. In this study, we performed an in-depth characterisation of MPs isolated from IS, caput-corpus and cauda epididymis of CX3CR1EGFP+/- mice that express EGFP in these cells. Flow cytometry analysis revealed region-specific subsets of MPs that express combinations of markers traditionally described in 'dendritic cells' or 'macrophages'. RNA sequencing identified distinct transcriptomic signatures in MPs from each region and revealed specific genes involved in inflammatory and anti-inflammatory responses, phagosomal activity and antigen processing and presentation. Functional fluorescent in vivo labelling assays showed that higher percentages of CX3CR1+ MPs that captured and processed antigens were detected in the IS compared to other regions. Confocal microscopy showed that in the IS, caput and corpus, circulatory antigens were internalised and processed by interstitial and intraepithelial MPs. However, in the cauda only interstitial MPs internalised and processed antigens, while intraepithelial MPs did not take up antigens, indicating that all antigens have been captured before they reached the epithelial lining. Cauda MPs may thus confer a stronger protection against blood-borne pathogens compared to proximal regions. By identifying immunoregulatory mechanisms in the epididymis, our study may lead to new therapies for male infertility and epididymitis and identify potential targets for immunocontraception.

Purinergic Signaling in Endometriosis-Associated Pain

Endometriosis is an estrogen-dependent gynecological disease, with an associated chronic inflammatory component, characterized by the presence of endometrial tissue outside the uterine cavity. Its predominant symptom is pain, a condition notably altering the quality of life of women with the disease. This review is intended to exhaustively gather current knowledge on purinergic signaling in endometriosis-associated pain. Altered extracellular ATP hydrolysis, due to changes in ectonucleotidase activity, has been reported in endometriosis; the resulting accumulation of ATP in the endometriotic microenvironment points to sustained activation of nucleotide receptors (P2 receptors) capable of generating a persistent pain message. P2X3 receptor, expressed in sensory neurons, mediates nociceptive, neuropathic, and inflammatory pain, and is enrolled in endometriosis-related pain. Pharmacological inhibition of P2X3 receptor is under evaluation as a pain relief treatment for women with endometriosis. The role of other ATP receptors is also discussed here, e.g., P2X4 and P2X7 receptors, which are involved in inflammatory cell–nerve and microglia–nerve crosstalk, and therefore in inflammatory and neuropathic pain. Adenosine receptors (P1 receptors), by contrast, mainly play antinociceptive and anti-inflammatory roles. Purinome-targeted drugs, including nucleotide receptors and metabolizing enzymes, are potential non-hormonal therapeutic tools for the pharmacological management of endometriosis-related pain.

Investigation of epididymal proteins and general sperm membrane characteristics of Formosan pangolin (Manis pentadactyla pentadactyla)

Background

Formosan Pangolin (Manis pentadactyla pentadactyla) is one of the three subspecies of Chinese pangolins, it is also an isolated sub-species naturally habitat in Taiwan. Despite earlier report on successful breeding of Sunda (Manis javanica) pangolin, breeding of Formosan pangolins in zoo captive populations is still challenging due to unknown reproductive characterizations of this species in both male and female populations.

Results

We characterized for the first time, reproductive tract of male Formosan pangolin. We showed pangolin epididymis was a collagen-enriched organ with apparent segmented sub-regions similar to other mammals. However, unlike most mammals exhibited two V-ATPase subunits, Formosan pangolin exhibited only V-ATPase subunit 2. This specific V-ATPase subunit extended its cellular localization throughout the cytoplasm of epididymal clear cells, suggesting pH regulation of luminal microenvironment might be different from other mammals. Electron micrographs showed rod-shaped pangolin sperm cells with multi-lamellar membrane structure at the sperm head. Similar to well-defined capacitation and acrosome reaction membrane changes in other mammals, we reported three distinct patterns (homogenous, punctuated and faded) of pangolin sperm head membrane changes. The concurrent increase in phosphotyrosine protein expression detected at the sperm mid-piece/tail and the emergence of punctuated membrane aggregates likely representing three sperm activation stages, namely inactivated, capacitated and acrosome reacted status of pangolin sperm.

Conclusion

By revealing unique epididymal V-ATPase distribution and sperm membrane dynamics in Formosan pangolin, we would understand better the fundamental aspects of reproduction parameters of Formosan pangolin.

The Involvement of the Chemokine RANTES in Regulating Luminal Acidification in Rat Epididymis

Background

A complex interplay between different cell types in the epithelium leads to activation of the luminal acidifying capacity of the epididymis, a process that is crucial for sperm maturation and storage. Basal cells sense the luminal angiotensin II (ANG II) and stimulate proton secretion in clear cells through nitric oxide (NO). Our previous study has shown the chemokine regulated upon activation normal T-cell expressed and secreted (RANTES) was expressed in the F4/80 positive macrophages of human epididymis. The objective of this study was to explore the involvement of RANTES in regulating the luminal acidification in the rat epididymis.

Methods

The role of RANTES was investigated by in vivo perfusion with recombinant RANTES, Met-RANTES, and PBS of different pH values. Furthermore, rats vasectomy was performed to alter the epididymal luminal pH. RIA was used to measure the tissue homogenate ANG II concentration. Real time-PCR and western blot were employed to examine the expression levels of AGTR2, RANTES, CCR1, CCR5, and iNOS in epididymis.

Results

RANTES was restricted to the basal macrophages of epididymal ducts and co-localized with its receptors CCR1 and CCR5. Both V-ATPase and iNOS were up-regulated in the cauda epididymis after perfused with recombinant RANTES, while the antagonist Met-RANTES perfusion led to a complete abrogation of the increased expression of V-ATPase in the apical membrane of clear cells and iNOS in macrophages. Upon alkaline perfusion, RANTES expression was significantly increased and the apical accumulation of V-ATPase in the clear cells was induced in the cauda epididymis. The luminal pH in the cauda epididymis increased after vasectomy. The concentration of the ANG II and the expression levels of AGTR2, RANTES, CCR1, CCR5, and iNOS dropped in the cauda epididymis following vasectomy.

Conclusion

Upon the activation of basal cells, RANTES might induce the NO release from macrophages by interacting with its receptors, which increases proton secretion by adjacent clear cells. Thus, RANTES is possible to participate in the crosstalk among basal cells, macrophages and clear cells for the fine control of an optimum acidic luminal environment that is critical for male fertility.

Changes in porcine cauda epididymal fluid proteome by disrupting the HPT axis: Unveiling potential mechanisms of male infertility

Male infertility or subfertility is frequently associated with disruption of the hypothalamic-pituitary-testis axis events, like secondary hypogonadism. However, little is known how this condition affects the proteomic composition of the epididymal fluid. In the present study, we evaluated the proteomic changes in the cauda epididymal fluid (CEF) in a swine model of secondary hypogonadism induced by anti-GnRH immunization using multidimensional protein identification technology. Seven hundred and eighteen proteins were identified in both GnRH-immunized and control groups. GnRH immunization doubled the number of proteins in the CEF, with 417 proteins being found exclusively in samples from GnRH-immunized boars. CEF from GnRH-immunized boars presented an increase in the number of proteins related to cellular and metabolic processes, with affinity to organic cyclic compounds, small molecules, and heterocyclic compounds, as well changed the enzymatic profile of the CEF. Also, a significant increase in the number of proteins associated to the ubiquitin-proteasome system was identified in CEF from GnRH-immunized animals. These results bring strong evidence of the impact of secondary hypogonadism on the epididymal environment, which is responsible for sperm maturation and storage prior ejaculation. Finally, the differently expressed proteins in the CEF are putative seminal biomarkers for testicular and epididymal disorders caused by secondary hypogonadism.

Novel role of proton-secreting epithelial cells in sperm maturation and mucosal immunity

Epithelial cells are immune sensors and mediators that constitute the first line of defense against infections. Using the epididymis, a model for studying tubular organs, we uncovered a novel and unexpected role for professional proton-secreting 'clear cells' in sperm maturation and immune defense. The epididymal epithelium participates in the maturation of spermatozoa via the establishment of an acidic milieu and transfer of proteins to sperm cells, a poorly characterized process. We show that proton-secreting clear cells express mRNA transcripts and proteins that are acquired by maturing sperm, and that they establish close interactions with luminal spermatozoa via newly described 'nanotubes'. Mechanistic studies show that injection of bacterial antigens in vivo induces chemokine expression in clear cells, followed by macrophage recruitment into the organ. Injection of an inflammatory intermediate mediator (IFN-γ) increased Cxcl10 expression in clear cells, revealing their participation as sensors and mediators of inflammation. The functional diversity adopted by clear cells might represent a generalized phenomenon by which similar epithelial cells decode signals, communicate with neighbors and mediate mucosal immunity, depending on their precise location within an organ.

Epithelial dynamics in the epididymis: role in the maturation, protection, and storage of spermatozoa

Epithelial cells line the lumen of tubular organs and are key players in their respective functions. They establish a unique luminal environment by providing a protective barrier and by performing vectorial transport of ions, nutrients, solutes, proteins, and water. Complex intercellular communication networks, specific for each organ, ensure their interaction with adjacent epithelial and non-epithelial cells, allowing them to respond to and modulate their immediate environment. In the epididymis, several epithelial cell types work in a concerted manner to establish a luminal acidic milieu that is essential for the post-testicular maturation and storage of spermatozoa. The epididymis also prevents autoimmune responses against auto-antigenic spermatozoa, while ensuring protection against ascending and blood pathogens. This is achieved by a network of immune cells that are in close contact and interact with epithelial cells. This review highlights the coordinated interactions between spermatozoa, basal cells, principal cells, narrow cells, clear cells, and immune cells that contribute to the maturation, protection, selection, and storage of spermatozoa in the lumen of the epididymis.