The composition of fluid collected by micropuncture and catheterization from the seminiferous tubules and rete testis of rats

Collective cell dynamics and luminal fluid flow in the epididymis: A mechanobiological perspective

BACKGROUND

The mammalian epididymis is a specialized duct system that serves a critical role in sperm maturation and storage. Its distinctive, highly coiled tissue morphology provides a unique opportunity to investigate the link between form and function in reproductive biology. Although recent genetic studies have identified key genes and signaling pathways involved in the development and physiological functions of the epididymis, there has been limited discussion about the underlying dynamic and mechanical processes that govern these phenomena.

AIMS

In this review, we aim to address this gap by examining two key aspects of the epididymis across its developmental and physiological phases.

RESULTS AND DISCUSSION

First, we discuss how the complex morphology of the Wolffian/epididymal duct emerges through collective cell dynamics, including duct elongation, cell proliferation, and arrangement during embryonic development. Second, we highlight dynamic aspects of luminal fluid flow in the epididymis, essential for regulating the microenvironment for sperm maturation and motility, and discuss how this phenomenon emerges and interplays with epididymal epithelial cells.

CONCLUSION

This review not only aims to summarize current knowledge but also to provide a starting point for further exploration of mechanobiological aspects related to the cellular and extracellular fluid dynamics in the epididymis.

Cellular Distribution of Aquaporin 3, 7 and 9 in the Male Reproductive System: A Lesson from Bovine Study (Bos taurus)

The increasing incidence of male infertility in humans and animals creates the need to search for new factors that significantly affect the course of reproductive processes. Therefore, the aim of this study was to determine the temporospatial expression of aquaglyceroporins (AQP3, AQP7 and AQP9) in the bovine (Bos taurus) reproductive system using immunohistochemistry and Western blotting. The study also included morphological analysis and identification of GATA-4. In brief, in immature individuals, AQP3 and AQP7 were found in gonocytes. In reproductive bulls, AQP3 was observed in spermatocytes and spermatogonia, while AQP7 was visible in all germ cells and the Sertoli cells. AQP7 and AQP9 were detected in the Leydig cells. Along the entire epididymis of reproductive bulls, aquaglyceroporins were visible, among others, in basal cells (AQP3 and AQP7), in epididymal sperm (AQP7) and in the stereocilia of the principal cells (AQP9). In males of all ages, aquaglyceroporins were identified in the principal and basal cells of the vas deferens. An increase in the expression of AQP3 in the testis and cauda epididymis and a decrease in the abundance of AQP7 in the vas deferens with age were found. In conclusion, age-related changes in the expression and/or distribution patterns of AQP3, AQP7 and AQP9 indicate the involvement of these proteins in the normal development and course of male reproductive processes in cattle.

Comparing the adult and pre-pubertal testis: Metabolic transitions and the change in the spermatogonial stem cell metabolic microenvironment

BACKGROUND

Survivors of childhood cancer often suffer from infertility. While sperm cryopreservation is not feasible before puberty, the patient's own spermatogonial stem cells could serve as a germ cell reservoir, enabling these patients to father their own children in adulthood through the isolation, in vitro expansion, and subsequent transplantation of spermatogonial stem cells. However, this approach requires large numbers of stem cells, and methods for successfully propagating spermatogonial stem cells in the laboratory are yet to be established for higher mammals and humans. The improvement of spermatogonial stem cell culture requires deeper understanding of their metabolic requirements and the mechanisms that regulate metabolic homeostasis.

AIM

This review gives a summary on our knowledge of spermatogonial stem cell metabolism during maintenance and differentiation and highlights the potential influence of Sertoli cell and stem cell niche maturation on spermatogonial stem cell metabolic requirements during development.

RESULTS AND CONCLUSIONS

Fetal human spermatogonial stem cell precursors, or gonocytes, migrate into the seminiferous cords and supposedly mature to adult stem cells within the first year of human development. However, the spermatogonial stem cell niche does not fully differentiate until puberty, when Sertoli cells dramatically rearrange the architecture and microenvironment within the seminiferous epithelium. Consequently, pre-pubertal and adult spermatogonial stem cells experience two distinct niche environments potentially affecting spermatogonial stem cell metabolism and maturation. Indeed, the metabolic requirements of mouse primordial germ cells and pig gonocytes are distinct from their adult counterparts, and novel single-cell RNA sequencing analysis of human and porcine spermatogonial stem cells during development confirms this metabolic transition. Knowledge of the metabolic requirements and their changes and regulation during spermatogonial stem cell maturation is necessary to implement laboratory-based techniques and enable clinical use of spermatogonial stem cells. Based on the advancement in our understanding of germline metabolism circuits and maturation events of niche cells within the testis, we propose a new definition of spermatogonial stem cell maturation and its amendment in the light of metabolic change.

The association of ODF4 with AK1 and AK2 in mice is essential for fertility through its contribution to flagellar shape

Normal sperm flagellar shape and movement are essential for fertilization. The integral protein outer dense fiber 4 (ODF4) localizes to ODFs, but its function remains unclear. Adenylate kinase (AK) is a phosphotransferase that catalyzes the interconversion and controls the concentration equilibrium of adenine nucleotides. AK shuttles ATP to energy-consuming sites. Here, we report on the relationship of flagellar shape and movement with ODF4, AK1 and AK2 by using Odf4-deletion (Odf4^-/-) mice. Soluble ODF4 is coimmunoprecipitated with AK1 and AK2 in Odf4^+/+ spermatozoa. ODF4, AK1 and AK2 localize to whole flagella (plasmalemma, mitochondria, ODFs, and residual cytoplasmic droplets (CDs)), principal pieces, and midpieces, respectively. Odf4^-/- sperm flagella lose ODF4 and reduce AK1 and AK2 but produce ATP. The flagellum is bent (hairpin flagellum) with a large CD in the midpiece. There is no motility in the midpiece, but the principal piece is motile. Odf4^-/- spermatozoa progress backward and fail to ascend in the uterus. Thus, Odf4^-/- males are infertile owing to abnormal flagellar shape and movement caused mainly by the loss of ODF4 with AK1 and AK2. This study is supported by the rescue experiment; the abnormalities and male infertility caused by Odf4 deletion were reversed by Odf4 restoration.

SOX17-positive rete testis epithelium is required for Sertoli valve formation and normal spermiogenesis in the male mouse

Seminiferous tubules (STs) in the mammalian testes are connected to the rete testis (RT) via a Sertoli valve (SV). Spermatozoa produced in the STs are released into the tubular luminal fluid and passively transported through the SV into the RT. However, the physiological functions of the RT and SV remain unclear. Here, we identified the expression of Sox17 in RT epithelia. The SV valve was disrupted before puberty in RT-specific Sox17 conditional knockout (Sox17-cKO) male mice. This induced a backflow of RT fluid into the STs, which caused aberrant detachment of immature spermatids. RT of Sox17-cKO mice had reduced expression levels of various growth factor genes, which presumably support SV formation. When transplanted next to the Sox17⁺ RT, Sertoli cells of Sox17-cKO mice reconstructed the SV and supported proper spermiogenesis in the STs. This study highlights the novel and unexpected modulatory roles of the RT in SV valve formation and spermatogenesis in mouse testes, as a downstream action of Sox17.

Tissue hydraulics in reproduction

The development of functional eggs and sperm are critical processes in mammalian development as they ensure successful reproduction and species propagation. While past studies have identified important genes that regulate these processes, the roles of luminal flow and fluid stress in reproductive biology remain less well understood. Here, we discuss recent evidence that support the diverse functions of luminal fluid in oogenesis, spermatogenesis and embryogenesis. We also review emerging techniques that allow for precise quantification and perturbation of tissue hydraulics in female and male reproductive systems, and propose new questions and approaches in this field. We hope this review will provide a useful resource to inspire future research in tissue hydraulics in reproductive biology and diseases.

Perfusion in Organ-on-Chip Models and Its Applicability to the Replication of Spermatogenesis In Vitro

Organ/organoid-on-a-chip (OoC) technologies aim to replicate aspects of the in vivo environment in vitro, at the scale of microns. Mimicking the spatial in vivo structure is important and can provide a deeper understanding of the cell-cell interactions and the mechanisms that lead to normal/abnormal function of a given organ. It is also important for disease models and drug/toxin testing. Incorporating active fluid flow in chip models enables many more possibilities. Active flow can provide physical cues, improve intercellular communication, and allow for the dynamic control of the environment, by enabling the efficient introduction of biological factors, drugs, or toxins. All of this is in addition to the fundamental role of flow in supplying nutrition and removing waste metabolites. This review presents an overview of the different types of fluid flow and how they are incorporated in various OoC models. The review then describes various methods and techniques of incorporating perfusion networks into OoC models, including self-assembly, bioprinting techniques, and utilizing sacrificial gels. The second part of the review focuses on the replication of spermatogenesis in vitro; the complex process whereby spermatogonial stem cells differentiate into mature sperm. A general overview is given of the various approaches that have been used. The few studies that incorporated microfluidics or vasculature are also described. Finally, a future perspective is given on elements from perfusion-based models that are currently used in models of other organs and can be applied to the field of in vitro spermatogenesis. For example, adopting tubular blood vessel models to mimic the morphology of the seminiferous tubules and incorporating vasculature in testis-on-a-chip models. Improving these models would improve our understanding of the process of spermatogenesis. It may also potentially provide novel therapeutic strategies for pre-pubertal cancer patients who need aggressive chemotherapy that can render them sterile, as well asfor a subset of non-obstructive azoospermic patients with maturation arrest, whose testes do not produce sperm but still contain some of the progenitor cells.

The endoplasmic reticulum, calcium signaling and junction turnover in Sertoli cells

The endoplasmic reticulum (ER) forms a continuous network throughout morphologically differentiated Sertoli cells. It is an integral component of intercellular adhesion junctions in this cell type, as well as forming membrane contact sites with the plasma membrane and intracellular organelles. One of the major functions of the ER in cells generally is maintaining calcium homeostasis and generating calcium signals. In this review, we discuss what is currently known about the overall pattern of distribution of the ER in Sertoli cells and the location of calcium regulatory machinery in the various subdomains of the organelle. Current data are consistent with the hypothesis that calcium signaling by the ER of Sertoli cells may play a significant role in events related to junction remodeling that occur in the seminiferous epithelium during spermatogenesis.

Estradiol modulates Na(+) -dependent HCO3 (-) transporters altering intracellular pH and ion transport in human Sertoli cells: A role on male fertility?

BACKGROUND INFORMATION

Infertile men often present deregulation of serum estrogen levels. Notably, high levels of estradiol (E2) are associated with low sperm production and quality. Sertoli cells (SCs) are responsible for spermatogenesis maintenance and are major targets for the hormonal signalling that regulates this complex process.

RESULTS

In this study, we used primary cultures of human SCs and studied the localisation, expression and functionality of the Na(+) -dependent HCO3 (-) transporters by confocal microscopy, immunoblot, epifluorescence and voltage clamp after 24 h of exposure to E2 (100 nM). All studied transporters were identified in human SCs. In E2-treated human SCs, there was an increase in NBCn1, NBCe1 and NDCBE protein levels, as well as an increase in intracellular pH and a decrease in transcellular transport.

CONCLUSIONS

We report an association between increased levels of E2 and the expression/function of Na(+) -dependent HCO3 (-) transporters in human SCs. Our results provide new evidence on the mechanisms by which E2 can regulate SCs physiology and consequently spermatogenesis. These mechanisms may have an influence on male reproductive potential and help to explain male infertility conditions associated with estrogen deregulation.

SIGNIFICANCE

Exposure to E2 increased human SCs intracellular pH. E2 is a modulator of ionic transcellular transport in human SCs.

Perspectives in Pediatric Pathology, Chapter 11. Testicular Pathology of Hamartomatous Origin

The term hamartoma was coined by Albrecht in 1904 from the Greek μαρτ-άνω, to go wrong [ 1 ]. Hamartoma is currently used to name nonneoplastic lesions composed of disorganized tissue indigenous to the site where it is found. In the testis, this refers to abnormal/excessive development of structures that usually form part of the gonadal parenchyma, epididymis, or spermatic cord. We include the following as hamartomatous lesions of the testis and sperm excretory ducts: cystic dysplasia of the rete testis, rete testis hamartomas, fetal gonadoblastoid testicular dysplasia (FGTD), Sertoli cell nodules, tubular hamartomas, congenital testicular and epididymal lymphangiectasis, and smooth muscle hyperplasia of paratesticular structures. These hamartomas are always benign, but their importance resides in their association with specific disorders, or as markers of complex syndromes.

Differential permeability of the blood-testis barrier during reinitiation of spermatogenesis in adult male rats

The blood-testis barrier (BTB) sequesters meiotic spermatocytes and differentiating spermatids away from the vascular environment. We aimed to assess whether meiosis and postmeiotic differentiation could occur when the BTB is permeable. Using a model of meiotic suppression and reinitiation, BTB function was assessed using permeability tracers of small, medium, and large (0.6-, 70-, and 150-kDa) sizes to emulate blood- and lymphatic-borne factors that could cross the BTB. Adult rats (n = 9/group) received the GnRH antagonist acyline (10 wk) to suppress gonadotropins, followed by testosterone (24cm Silastic implant), for 2, 4, 7, 10, 15, and 35 days. In acyline-suppressed testes, all tracers permeated the seminiferous epithelium. As spermatocytes up to diplotene stage XIII reappeared, both the 0.6- and 70-kDa tracers, but not 150 kDa, permeated around these cells. Intriguingly, the 0.6- and 70-kDa tracers were excluded from pachytene spermatocytes at stages VII and VIII but not in subsequent stages. The BTB became progressively impermeable to the 0.6- and 70-kDa tracers as stages IV-VII round spermatids reappeared in the epithelium. This coincided with the appearance of the tight junction protein, claudin-12, in Sertoli cells and at the BTB. We conclude that meiosis can occur when the BTB is permeable to factors up to 70 kDa during the reinitiation of spermatogenesis. Moreover, BTB closure corresponds with the presence of particular pachytene spermatocytes and round spermatids. This research has implications for understanding the effects of BTB dynamics in normal spermatogenesis and also potentially in states where spermatogenesis is suppressed, such as male hormonal contraception or infertility.

Maturation of sperm volume regulation in the rat epididymis

Sperm maturation in the epididymis may involve differences between mature and immature spermatozoa in their volume regulatory osmolyte response. Spermatozoa obtained from the rat caput and cauda epididymidis were examined for their ability to regulate volume after transfer from in situ epididymal osmolality (measured to be 343 +/- 13 and 365 +/- 19 mmol kg(-1), respectively) to that of the female tract in single- and multiple-step protocols. Cells withstood the single-step treatment better than the multistep protocol. Sperm volume estimates by flow cytometric measurements of forward scatter of cells with intact head membranes was more sensitive than those by assessing cell coiling microscopically. At osmolalites below 210 mmol kg(-1) both caput and cauda cells ruptured, limiting the use of flow cytometry. Above this critical value, the use of quinine showed that both caput and cauda cells could regulate volume, but cauda cells were the more effective. Of several organic osmolytes studied, myo-inositol, glutamate and KCl caused only temporary and slight swelling of spermatozoa cells in hypotonic medium. Spermatozoa of both maturities seemed to use potassium as the preferred osmolyte for regulating volume.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

Impermeability of sertoli cell junctions to prolonged exposure to peroxidase

The competence of the occluding junctional complexes between Sertoli cell has been studied after continuous exposure of the testis to a high concentration of peroxidase for periods of 30 minutes to 4 hours. Horseradish peroxidase in buffered saline solution (10 mg/ml) infused through an indwelling polyethelene tube implanted interstitially in the testis becomes widely distributed throughout the organ via the extensive system of lymphatic sinusoids. All the components of the testicular interstitium become heavily infiltrated. A large amount of peroxidase accumulates in the acellular layers of the lamina propria of the seminiferous tubules. Some traverses patent intercellular clefts between myoid cells and enters the interspaces of the basal compartment of the epithelium. The Sertoli cell junctions effectively prevent any further penetration of peroxidase toward the adluminal compartment and in no case was the tracer observed in the tubular lumen. The present study extends previous observations based on brief exposure to tracers and confirms the conclusion that the occluding Sertoli cell junctions are highly impermeable to small tracers and constitute the main structural component of the blood-testis barrier.

Intracellular pH regulation in human Sertoli cells: role of membrane transporters

Sertoli cells are responsible for regulating a wide range of processes that lead to the differentiation of male germ cells into spermatozoa. Intracellular pH (pHi) is an important parameter in cell physiology regulating namely cell metabolism and differentiation. However, pHi regulation mechanisms in Sertoli cells have not yet been systematically elucidated. In this work, pHi was determined in primary cultures of human Sertoli cells. Sertoli cells were exposed to weak acids, which caused a rapid acidification of the intracellular milieu. pHi then recovered by a mechanism that was shown to be particularly sensitive to the presence of the inhibitor DIDS (4,4′-diisothiocyanostilbene disulfonic acid). In the presence of amiloride and PSA (picrylsulfonic acid), pHi recovery was also significantly affected. These results indicate that, in the experimental conditions used, pHi is regulated by the action of an Na+-driven HCO3−/Cl−exchanger and an Na+/HCO3−co-transporter and also by the action of the Na+/H+exchanger. On the other hand, pHi recovery was only slightly affected by concanamycin A, suggesting that V-Type ATPases do not have a relevant action on pHi regulation in human Sertoli cells, and was independent of the presence of bumetanide, suggesting that the inhibition of the Na+/K+/Cl−co-transporter does not affect pHi recovery, not even indirectly via the shift of ionic gradients. Finally, pHi was shown to be sensitive to the removal of external Cl−, but not of Na+or K+, evidencing the presence of a membrane Cl−-dependent base extruder, namely the Na+-independent HCO3−/Cl−exchanger, and its role on pHi maintenance on these cells.

Testicular descent, sperm maturation and capacitation. Lessons from our most distant relatives, the monotremes

The present review examines whether monotremes may help to resolve three questions relating to sperm production in mammals: why the testes descend into a scrotum in most mammals, why spermatozoa are infertile when they leave the testes and require a period of maturation in the specific milieu provided by the epididymides, and why ejaculated spermatozoa cannot immediately fertilise an ovum until they undergo capacitation within the female reproductive tract. Comparisons of monotremes with other mammals indicate that there is a need for considerable work on monotremes. It is hypothesised that testicular descent should be related to epididymal differentiation. Spermatozoa and ova from both groups share many of the proteins that are thought to be involved in gamete interaction, and although epididymal sperm maturation is significant it is probably less complex in monotremes than in other mammals. However, the monotreme epididymis is unique in forming spermatozoa into bundles of 100 with greatly enhanced motility compared with individual spermatozoa. Bundle formation involves a highly organised interaction with epididymal proteins, and the bundles persist during incubation in vitro, except in specialised medium, in which spermatozoa separate after 2–3 h incubation. It is suggested that this represents an early form of capacitation.

The testis in immune privilege

The production, differentiation, and presence of male gametes represent inimitable challenges to the immune system, as they are unique to the body and appear long after the maturation of the immune system and formation of systemic self-tolerance. Known to protect germ cells and foreign tissue grafts from autoimmune attack, the 'immune privilege' of the testis was originally, and somewhat simplistically, attributed to the existence of the blood-testis barrier. Recent research has shown a previously unknown level of complexity with a multitude of factors, both physical and immunological, necessary for the establishment and maintenance of the immunotolerance in the testis. Besides the blood-testis barrier and a diminished capability of the large testicular resident macrophage population to mount an inflammatory response, it is the constitutive expression of anti-inflammatory cytokines in the testis by immune and particularly somatic cells, that represents an essential element for local immunosuppression. The role of androgens in testicular immune regulation has long been underestimated; yet, accumulating evidence now shows that they orchestrate the inhibition of proinflammatory cytokine expression and shift cytokine balance toward a tolerogenic environment. Furthermore, the role of the testicular dendritic cells in suppressing antigen-specific immunity and T-lymphocyte activation is discussed. Finally, the active role mast cells play in the induction and amplification of immune responses, both in infertile humans and in experimental models, highlights the importance of preventing mast cell activation to maintain the immune-privileged status of the testis.

KCNQ1/KCNE1 channels during germ-cell differentiation in the rat: expression associated with testis pathologies

KCNQ1/KCNE1 channels are responsible for the Jervell-Lange-Nielsen cardiac syndrome, which is also characterized by congenital deafness. KCNQ1/KCNE1 is crucial for K+ transport in the inner ear. We show that KCNQ1 and KCNE1 are associated in testis and that their expression is closely regulated during development. Both genes were expressed in undifferentiated germ cells in 21-day-old rats and mostly confined to basal immature germ cells in adulthood. Leydig and Sertoli cells were negative. KCNQ1 and KCNE1 were also studied in various germ-cell pathologies. First, in spontaneous unilateral rat testis atrophy, hematoxylin-eosin analysis revealed massive germ-cell aplasia with only Sertoli cells and groups of interstitial Leydig cells. In these samples, KCNQ1 and KCNE1 were not expressed. In human seminoma samples characterized by a proliferation of undifferentiated germ cells, KCNQ1/KCNE1 protein levels were higher than in healthy samples. Our results demonstrate that the expression of KCNQ1 and KCNE1 is associated with early stages of spermatogenesis and with the presence of undifferentiated healthy or neoplastic germ cells. The presence of a K+ rich-fluid in the seminiferous tubule suggests that KCNQ1/KCNE1 is involved in K+ transport, probably during germ-cell development.

Composition of Luminal Fluid Secreted by the Seminiferous Tubules and After Reabsorption by the Extratesticular Ducts of the Japanese Quail, Coturnix coturnix japonica1

The present report examines the composition of luminal fluid in the seminiferous tubule (STF), rete testis (RTF), and ductus epididymidis of the Japanese quail (Coturnix coturnix japonica). This subject is of particular interest, both because the reproductive ducts are intra-abdominal and because sperm production is more rapid in birds than in mammals. It was interpreted that micropuncture samples of STF contain varying amounts of contamination with intracellular solute, particularly K and protein. The concentration of solute in samples was correlated with packed cell volume (spermatocrit), and when the latter was used to assess estimates of solute concentration in STF, the magnitude of the estimates were much the same as determinations in RTF. Consequently, it is concluded that the fluid entering the rete testis of the quail is the primary secretion of the seminiferous tubules. The composition of RTF in the quail was determined to be 148 mM Na, 126 mM Cl, 9.8 mM K, 2.7 mM Mg, 1.4 mM Ca, 2.1 mM glutamate, 3.4 mM glutamine, 20.2 mM bicarbonate, 1.8 microg microl(-1) of protein, pH 7.34, and 310 mmol kg(-1), and it is significantly different from the composition of blood plasma. Estimates of solute output by the testis and reabsorption by the extratesticular ducts indicate, first, that most of the solutes secreted into the seminiferous tubules are subsequently reabsorbed from the extratesticular ducts and, second, that sufficient solute of testicular origin (except for protein) exists to account for the concentrations of solutes throughout the lumen of the duct system. Changes in the concentration of solute in the extratesticular ducts probably result from different reabsorption rates of solute and water. The composition of fluid from the distal end of the ductus epididymidis was 133 mM Na, 125 mM Cl, 25 mM K, 1.0 mM Mg, 0.3 mM Ca, 6.7 mM glutamate, 4.0 mM glutamine, 19.5 mM bicarbonate, 6.0 microg microl(-1) of protein, pH 7.33, and 335 mmol kg(-1), and it is significantly different from those of RTF and blood.

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.

Fluid Reabsorption by the Ductuli Efferentes Testis of the Rat Is Dependent on Both Sodium and Chlorine1

The role of Na(+) and Cl(-) in fluid reabsorption by the efferent ducts was examined by perfusing individual ducts in vivo with preparations of 160 mM NaCl in which the ions were replaced, together or individually, with organic solutes while maintaining the osmolality at 300 mmol/kg. Progressively replacing NaCl with mannitol reduced net reabsorption of water and the ions in a concentration-dependent manner, and caused net movement into the lumen at concentrations of NaCl less than 80 mM. The net rates of flux were lower for Na(+) than for Cl(-). In collectates, [Na(+)] was greater than [Cl(-)], indicating that Cl(-) transport is probably linked with another anion. Replacing either Na(+) or Cl(-) in perfusates (with choline and isethionate, respectively) while maintaining the other inorganic ion at 160 mM also reduced net rates of reabsorption in a concentration-dependent manner to zero when either ion was completely replaced. There were no significant differences in the osmolality of perfusate and collectate, and collectates contained a mean of 3.4 mM K(+), indicating a backflux of K(+) into the lumen. It is concluded that fluid reabsorption from the efferent ducts is dependent on the transport of both Na(+) and Cl(-) from the lumen (from a luminal concentration of at least 70-80 mM), and that Cl(-) transport is dependent on another anion. The epithelium is permeable to K(+) and has a higher permeability to a range of organic solutes (mannitol, choline, and isethionate) than epithelium in the proximal kidney tubules.

Immunohistochemical investigations of the autonomous innervation of the cervine testis

The innervation of the cervine testis was studied in 6 roe deers, 7 red deers and 14 fallow deers. The results for the three species are rather similar. With anti-sera to neurofilament (NF) and neuron specific enolase (NSE), all small and large nerve fascicles can be demonstrated, but single fibers are incompletely stained. Immunoreactions against protein gene product-9.5 (PGP-9.5) and GAP-43 (growth-associated protein-43) are better suited to depict the complete innervation pattern. Bundles of the superior spermatic and inferior spermatic nerves reach the testis via three access routes as funicular, mesorchial and caudal nerve contributions. We found no morphological evidence that the nerves in the cervine testis are directly involved in regulating Leydig cell function or seminiferous tubular motility. The majority of the testicular nerves are associated with the testicular arteries, but the musculature in the walls of the venous plexus pampiniformis is also innervated. All vascular nerve fibers represent postjunctional sympathetic axons displaying a strong dopamine-beta-hydroxylase (DBH) activity, mostly co-expressed with neuropeptide Y (NPY). The presence of cholinergic fibers in the testis of the deer is only sporadic and probably of no functional importance. In all three species of deer, a small quantity of myelinated nerve fibers is encountered in spermatic cord and tunica albuginea and regarded as afferent. The viscerosensory quality in the testicular intrinsic innervation is very likely mediated by the CGRP (calcitonin gene-related peptide)-positive fibers that run independently from the testicular vessels and end in the connective tissue of spermatic cord and tunica albuginea. The testis of the red deer contains significantly more VIP (vasoactive intestinal polypeptide)-positive axons than that of roe and fallow deer. The nerve density in the interior of the testicular lobules shows no regional differences, but there are age- and season-related changes that correlate with the developmental and functional state of the seminiferous tubules. Small testes with solid and narrow tubules, as seen in the prepuberal phase and during seasonal reproductive quiescence, are better innervated than large testes with expanded and spermatogenetically active seminiferous tubules.

Hormones: what the testis really sees

Various barriers in the testis may prevent hormones from readily reaching the cells they are supposed to stimulate, especially the hydrophilic hormones from the pituitary. For example, LH must pass through or between the endothelial cells lining the blood vessels to reach the surface of the Leydig cells, and FSH has the additional barrier of the peritubular myoid cells before it reaches the Sertoli cells. The specialised junctions between pairs of Sertoli cells would severely restrict the passage of peptides from blood to the luminal fluid and therefore to the cells inside this barrier, such as the later spermatocytes and spermatids. There is evidence in the literature that radioactively labelled LH does not pass readily into the testis from the blood, and the concentration of native LH in the interstitial extracellular fluid surrounding the Leydig cells in rats is only about one-fifth of that in blood plasma. Furthermore, after injection with LHRH, there are large rises in LH in the blood within 15 min, at which time the Leydig cells have already responded by increasing their content of testosterone, but with no significant change in the concentration of LH in the interstitial extracellular fluid. Either the Leydig cells respond to very small changes in LH, or the testicular endothelial cells in some way mediate the response of the Leydig cells to LH, for which there is now some evidence from co-cultures of endothelial and Leydig cells. The lipophilic steroid hormones, such as testosterone, which are produced by the Leydig cells, have actions within the seminiferous tubules in the testis but also in other parts of the body. They should pass more readily through cells than the hydrophilic peptides; however, the concentration of testosterone in the fluid inside the seminiferous tubules is less than in the interstitial extracellular fluid in the testis, especially after stimulation by LH released after injection of LHRH and despite the presence inside the tubules of high concentrations of an androgen-binding protein. The concentration of testosterone in testicular venous blood does not rise to the same extent as that in the interstitial extracellular fluid, suggesting that there may also be some restriction to movement of the steroid across the endothelium. There is a very poor correlation between the concentrations of testosterone in fluids from the various compartments of the testis and in peripheral blood plasma. Determination of the testosterone concentration in the whole testis is also probably of little predictive value, because the high concentrations of lipid in the Leydig cells would tend to concentrate testosterone there, and hormones inside these cells are unlikely to have any direct effect on other cells in the testis. The best predictor of testosterone concentrations around cells in the testis is the level of testosterone in testicular venous blood, the collection of which for testosterone analysis is a reasonably simple procedure in experimental animals and should be substituted for tissue sampling. There seems to be no simple way of determining the concentrations of peptide hormones in the vicinity of the testicular cells.

Characterization of the expression and regulation of genes necessary for myo-inositol biosynthesis and transport in the seminiferous epithelium

In many mammals, the concentration of myo-inositol in the fluid of the seminiferous tubules is dramatically higher than levels found in serum. Two enzymes involved in myo-inositol synthesis: myo-inositol-1-phosphate synthase (ISYNA1) and myo-inositol monophosphatase-1 (IMPA1), are known to have high activity in the testes. ISYNA1 is an isomerase that catalyzes the conversion of glucose-6-phoshate to myo-inositol-1-phosphate. IMPA1 then hydrolyzes the phosphate group to produce myo-inositol. Although no physiological role for the high concentration of myo-inositol has yet to be elucidated, it has been suggested that it could be involved in osmoregulation. Previous research on these enzymes in the testis has focused on enzyme activity. The objective of this study was to evaluate the expression of these genes and the myo-inositol transporter, Slc5a3, within the testis. Using Northern blot analyses, we found that all three genes, Impa1, Isyna1, and Slc5a3 are expressed in Sertoli cells. Isyna1 is highly expressed in two types of germ cells, pachytene spermatocytes and round spermatids. IMPA1 was expressed in round spermatids. Slc5a3 expression is upregulated when Sertoli cells are treated with 0.1 mM dibutyryl cAMP. When Sertoli cells were cultured in a hypertonic medium, there was an increase in the expression of Isyna1 and Slc5a3. We postulate that this upregulation is a result of the capability of the Sertoli cell to sense and then react to a change in osmolarity by increasing the transport and production of the osmolyte myo-inositol.

Are there two forms of beta 2-N-acetylglucosaminyltransferase I in rat testicular and epididymal fluids?

The activity of alpha 3-D-mannoside-beta-1,2-N-acetylglucosaminyltransferase I (GnT I; EC 2.4.1.101), which catalyzes the first step in the conversion of oligomannose to complex or hybrid N-glycans of glycoproteins, was detected in rat testicular and cauda epididymal fluids. The GnT I activity of testicular fluid had a pH optimum of 6.0, whereas that of the cauda epididymal fluid was optimal at pH 7.0. The enzyme in testicular fluid had an absolute requirement for either Co2+, or Mn2+, Mg2+ and Ca2+, the activity being stimulated by these cations in the above order, whereas that of cauda epididymal fluid had an absolute requirement for Mn2+ or Ca2+, with Co2+ and Mg2+ being ineffective. The specific activity of GnT I in cauda epididymal fluid was somewhat higher than in testicular fluid. The apparent Km value for alpha 1-3 alpha 1-6mannopentaose of GnT I in the testicular and epididymal fluids was 0.57 and 0.38 mM, respectively. The substrate specificity for both GnT I activities decreased in the following order: alpha1-3 alpha 1-6mannopentaose>alpha1-3 alpha 1-6mannotriose>alpha 1-3mannobiose>alpha 1-6mannobiose. These data suggest that two forms of GnT I exist in the testicular and epididymal fluids.

Germinal angiotensin I-converting enzyme is totally shed from the rodent sperm membrane during epididymal maturation

Acquisition of sperm fertilizing ability is due, in part, to the reorganization of plasma membrane proteins that occurs during epididymal sperm transit. Using polyclonal antibodies against angiotensin I-converting enzyme (ACE), we showed that this enzyme is immunolocalized mainly on the middle piece of rat and mouse testicular sperm and with less intensity along the initial part of the principal piece of the flagellum. In both species, only some sperm from the caput epididymis were still reactive, whereas no labeling was observed on cauda epididymal sperm. The 105- to 110-kDa germinal ACE was absent from the rat testicular fluid but appeared in the fluid of the anterior epididymis. Thereafter, its molecular weight shifted to 94 kDa in the corpus epididymal fluid and remained at this weight in the caudal region. The 105- to 110-kDa immunoreactive protein was present in testicular rat sperm extract but was completely absent from epididymal sperm extracts. Western blot analysis of testicular and epididymal tissue extracts from the rat and mouse also confirmed that the germinal enzyme was absent from the epididymal sperm cell. Our results demonstrated that the rodent germinal ACE is released from the testicular sperm membrane when sperm enter the epididymis, a process similar to that observed in domestic mammals. This result is discussed in view of the suggested role for this enzyme in sperm fertility.

Role of seminal osmolarity in the reduction of human sperm motility

Mammalian sperm at ejaculation are suspended in the seminal plasma, a heterogeneous mixture deriving from the testicular/epididymal fluid and from secretions of seminal vesicles, prostate and bulbourethral glands. Biochemical characteristics of seminal fluid change along the male reproductive tract when considering its inorganic and organic composition and pH but it is known that in each region of the male genital tract seminal osmolarity is higher than that of serum. It has been previously demonstrated that in invertebrate and vertebrate sperm, seminal plasma osmolarity influences sperm motility and activity, and human sperm have been shown to possess osmosensitive calcium entry pathway that controls important functions such as acrosome reaction and oocyte penetration. In the present study, we have determined seminal plasma osmolarity in a large number of normozoospermic fertile and asthenozoospermic infertile subjects correlating it with sperm motility percentages and kinematic characteristics determined utilizing a computerized motion analysis system. Our results confirm that seminal plasma osmolarity is higher than that of serum (336.1 +/- 20.2 vs. 291.1 +/- 6.9 mOsm/L, respectively). Normozoospermic subjects show seminal osmolarity values that are significantly lower with respect to asthenozoospermic patients (317.8 +/- 12.2 vs. 345.2 +/- 22.6 mOsm/L, p<0.001), irrespective of the cause of asthenozoospermia. Seminal plasma osmolarity negatively correlates with sperm progressive motility percentages and kinetic characteristics (curvilinear velocity, linear velocity, linear coefficient and lateral displacements of sperm head). Furthermore, when sperm from fertile subjects were suspended in medium with an osmolarity increasing from 300 to 600 mOsm, sperm motility percentages and kinetics characteristics were progressively reduced and nearly abolished when medium osmolarity was 600 mOsm. On the contrary, when sperm from asthenozoospermic subjects with high semen osmolarity were resuspended in medium with lower osmolarity, sperm motility parameters improved significantly. Sperm motility parameters did not correlate with seminal plasma concentrations of sodium, potassium, chloride with a weak correlation only with seminal calcium concentration. No correlations are present between seminal plasma osmolarity and ionic composition. In conclusion, the present study confirms and extends the knowledge that, in human, seminal plasma osmolarity is higher than that of serum and demonstrates that seminal osmolarity influences sperm motility characteristics and then it may contribute to the pathogenesis of some forms of asthenozoospermia and male infertility.

New light shed on fluid formation in the seminiferous tubules of the rat

In this study the effects of perfusing isolated seminiferous tubules of the testes are reported for the first time. Initial perfusion studies (fast rate perfusion) resulted in gross morphological damage to the seminiferous tubules. The recorded transepithelial potential (V(t)) was close to 0 mV. Slow perfusion rates eliminated morphological damage to the perfused tubules. These tubules exhibited a V(t) of -5.4 +/- 1.8 mV which was significantly different (P < 0.0001) from tubules that were perfused at a fast rate. Additional non-perfusion electrophysiological experiments (oil-gap and agar probe techniques) provided the confirmation that tubules not morphologically compromised produced a higher V(t) which was not statistically different (P < 0.0001) from slowly perfused tubules. A revised hypothesis on fluid secretion is postulated. In brief, that the seminiferous tubule is solely responsible for the production of its luminal fluid. This hypothesis is contrary to the long standing 'Tuck' hypothesis which suggested that the source of luminal fluid in the seminiferous tubule originated from secretions of Sertoli cells as well as from distal testicular structures, e.g. the rete testis.

Identification and functional analysis of splice variants of the germ cell soluble adenylyl cyclase

In mammalian germ cells, cAMP signaling is dependent on two forms of adenylyl cyclase, the conventional membrane-bound ACIII and a soluble form of adenylyl cyclase (sAC). Recent elucidation of the sAC sequence indicates that this enzyme is phylogenetically distinct from the membrane-bound AC, does not interact with G proteins, and its activity is regulated by bicarbonate ions. Here we have investigated the properties and regulation of this enzyme during spermatogenesis. Two different transcripts encoding a full-length and truncated sAC were identified by reverse transcriptase-polymerase chain reaction and RNase protection analysis. The truncated sAC transcript lacks exon 11 with a premature termination of the open reading frame after the catalytic domain. Reverse transcriptase-polymerase chain reaction with testis RNA from adult mouse and rat of different ages, as well as RNase protection, showed that both transcripts are absent at 11 days of age, appear between 20 and 30 days of age, and are retained in the adult testis. The presence of corresponding proteins in testis, germ cells, and spermatozoa was demonstrated by fast protein liquid chromatography and differential immunoprecipitation with full-length sAC-specific antibodies. Bicarbonate ions activated both sAC forms and increased cAMP levels in germ cells isolated from 25- and 50-day-old rats and adult rats in a concentration-dependent manner. These findings provide evidence that full-length and truncated sAC are generated by alternate splicing. Both forms are active in spermatids, and the bicarbonate present in the seminiferous tubule may be a signal that regulates cAMP levels in these cells.

Failure of spermatogenesis in mouse lines deficient in the Na(+)-K(+)-2Cl(-) cotransporter

The Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) carries 1 molecule of Na(+) and K(+) along with 2 molecules of Cl(-) across the cell membrane. It is expressed in a broad spectrum of tissues and has been implicated in cell volume regulation and in ion transport by secretory epithelial tissue. However, the specific contribution of NKCC1 to the physiology of the various organ systems is largely undefined. We have generated mouse lines carrying either of 2 mutant alleles of the Slc12a2 gene, which encodes this cotransporter: a null allele and a mutation that results in deletion of 72 amino acids of the cytoplasmic domain. Both NKCC1-deficient mouse lines show behavioral abnormalities characteristic of mice with inner ear defects. Male NKCC1-deficient mice are infertile because of defective spermatogenesis, as shown by the absence of spermatozoa in histological sections of their epididymides and the small number of spermatids in their testes. Consistent with this observation, we show that Slc12a2 is expressed in Sertoli cells, pachytene spermatocytes, and round spermatids isolated from wild-type animals. Our results indicate a critical role for NKCC1-mediated ion transport in spermatogenesis and suggest that the cytoplasmic domain of NKCC1 is essential in the normal functioning of this protein.

pH and bicarbonate in the ductuli efferentes testis of the rat

The pH and bicarbonate concentrations of luminal fluids in the efferent ducts of the rat were estimated from pH measurements of samples in vitro under conditions of controlled temperature and carbon dioxide tension. The pH of scrotal blood was estimated to be more acidic than systemic blood (mean pH=7.44) at either of the putative scrotal carbon dioxide tensions (5% and 7%, pH, respectively,=7.42 and 7.28). For PCO2 tensions of 5% and 7%, respectively, the data indicated that the pH in the efferent ducts was significantly higher (distal initial zone pH=7.55 or 7.41; coni vasculosi pH=7.66 or 7.51; p < 0.01) than in fluid entering (rete testis fluid, pH=7.34 or 7.20) or leaving the ducts (zone 1a of the epididymal duct 7.26 or 7.11). Bicarbonate concentrations were also significantly higher (p < 0.01) in the efferent ducts (35.4 +/- 4.7 mM, distal initial zone; 45.2 +/- 7.6 mM, coni vasculosi) than in fluids entering (22.9 +/- 3.6 mM) or leaving (20.4 +/- 4.9 mM) the ducts. Estimates of the reabsorption of bicarbonate and fluid indicated that 96% of the testicular output of bicarbonate was reabsorbed in the efferent ducts, but there was also some secretion of bicarbonate into the ducts. It is concluded that luminal pH and bicarbonate levels in the efferent ducts of the rat are high relative to those found in the epididymis where low pH and bicarbonate contributes to sperm quiescence during storage. Nevertheless, the high rate of bicarbonate reabsorption in the efferent ducts is a major contributor to the establishment of the low pH and bicarbonate milieu of the epididymis.

Regulated anion secretion in cultured epithelia from Sertoli cells of immature rats

1. Cultured epithelia of Sertoli cells from prepubertal rats were grown on Matrigel-coated millipore filters for short-circuit current (Isc) measurements. Under basal conditions, these epithelia exhibited a 'zero' transepithelial potential difference, a 'zero' short-circuit current and a transepithelial resistance of 60 Omega cm2. 2. Forskolin (100 microM) and 8-(4-chlorophenylthio)-cAMP (cpt-cAMP) (100 microM) added to the apical side stimulated the Isc (forskolin, peak DeltaIsc = 1.32 +/- 0.16 microA cm-1; cpt-cAMP, peak DeltaIsc = 0.88 +/- 0.16 microA cm-2). 3. ATP (100 microM) added apically elicited a Isc response (peak DeltaIsc = 6.45 +/- 0. 28 microA cm-2) which was similar in magnitude to that of 1 microM thapsigargin (peak DeltaIsc = 6.09 +/- 0.44 microA cm-2). The potency of the responses to other nucleotides: UTP >= ATP > ADP >> AMP = adenosine indicates the involvement of a mixture of P2Y receptors. 4. Removal of extracellular Cl- and HCO3- reduced the Isc response to ATP by 70 % and 40 %, respectively. Removal of K+ had no effect, whereas removal of Na+ attenuated the Isc response. 5. The response to ATP was insensitive to agents known to block anion secretion (except apical diphenylamine-2-carboxylate (DPC) and DIDS). The resistance to perturbation by pharmacological agents may be a unique property of the seminiferous epithelium. 6. Whole-cell current recordings in cultured rat Sertoli cells demonstrated a DIDS-sensitive outwardly rectifying Cl- conductance with activating and inactivating characteristics at depolarizing and hyperpolarizing voltages, respectively. 7. The stimulation of electrogenic ion transport by ATP may be part of a complex mechanism regulating fluid secretion by the testis. Cultured Sertoli cell epithelia are shown to provide a useful model to investigate transepithelial transport in the seminiferous epithelium.

Secretion of D-aspartic acid by the rat testis and its role in endocrinology of the testis and spermatogenesis

The D-isomer of aspartic acid (D-Asp) has been found in rat testes. In the present study, samples of testicular venous blood plasma, rete testis fluid, interstitial extracellular fluid, luminal fluid from the seminiferous tubules, testicular parenchymal cells, epididymal spermatozoa and peripheral blood plasma were collected and analyzed for D-Asp by two methods, an enzymatic and a chromatographic HPLC method. The two methods gave very similar results for all samples. The highest concentrations of D-Asp (about 120 nmol/ml) were found in testicular venous blood plasma, with slightly lower concentrations in rete testis fluid (95 nmol/ml) and epididymal spermatozoa (80 nmol/g wet weight). Lower levels were found in testicular parenchymal cells (which would comprise mostly spermatids and spermatocytes), luminal fluid from the seminiferous tubules and interstitial extracellular fluid (26, 23 and 11 nmol/ml respectively). However, these values were all higher than those for peripheral blood plasma (6 nmol/ml). It would appear that D-Asp is being secreted by the testis mostly into the venous blood, passing thence into the rete testis fluid and being incorporated into the spermatozoa at the time or after they leave the testis. The distribution of D-Asp is thus quite different from that of testosterone, and its role and the reason for its high concentration in the male reproductive tract remain to be elucidated.

Appearance of 'natural' antisperm autoantibodies after sexual maturation of normal Lewis rats

Serum antisperm antibodies were assessed quantitatively with an ELISA in normal male Lewis rats at intervals between ages 10 and 128 days, spanning the onset of puberty. Antisperm antibodies rose between 56 and 91 days, and were significantly higher in 91- and 128-day old rats than at earlier intervals. The animals underwent normal pubertal development as indicated by increases in weights of the seminal vesicles and ventral prostate. The rise in antisperm antibodies correlated temporally with events in the postnatal development of the male reproductive system, with the increase in antisperm antibodies most closely following the time when spermatozoa reach the epididymis and proximal vas deferens at approximately 56 days. The observation that serum antisperm antibodies increased only after sexual maturation suggests that some differentiation antigens of sperm are processed and presented to the immune system under normal circumstances in this strain. Western blot analysis showed that the sera from normal postpubertal Lewis rats bound several proteins, including bands of > 100, 82-75, 78, 68, 65, 63, 54-55, 42, 37, 35, 26, and 20-22 kDa. The majority of these autoantibodies were sperm-specific as shown by the absence of comigrating bands in western blots of somatic tissue extracts, although antibodies in postpubertal sera recognized certain other proteins in somatic tissues. Several protein autoantigens, defined by sera from postpubertal animals, matched dominant autoantigens recognized by antibodies produced in response to vasectomy, prepubertal vas obstruction, or immunization with spermatozoa. This finding indicates that the antisperm antibody responses following sperm immunization, vasectomy or prepubertal vasal obstruction represent accentuation of an autoantibody response to sperm that develops normally following puberty.

Production of the cysteine proteinase inhibitor cystatin C by rat Sertoli cells

The Sertoli cells of the rat testis produce cystatin C, a cysteine proteinase inhibitor. Primary culture of Sertoli cells secreted both unglycosylated and glycosylated forms of rat cystatin C. Despite the low concentration of cystatin C in rete testis fluid, equilibrium dissociation constants (Ki) for the interaction between cystatin C and lysosomal cathepsins indicate that this molecule could be involved in the local regulation of testicular cysteine proteinase activity which may be necessary for spermatogenesis and spermiogenesis.