Role of the epididymis in mediating changes in the male gamete during maturation

Endoplasmic reticulum stress increases exosome biogenesis and packaging relevant to sperm maturation in response to oxidative stress in obese mice

BACKGROUND

Mammalian sperm maturation in the epididymis is mainly modulated by exosomes that are secreted into the epididymal lumen from epididymal epithelial cells (EECs). Exposure to oxidative stress (OS) resulting from being fed a high fat diet (HFD) reduces sperm fertility, which is one of the cause inducing male infertility. Thus, we hypothesize that stress-induced changes in exosome content play a critical role in mediating this detrimental process.  METHODS: An obese mouse model was established by feeding a HFD. Then oxidative stress status was measured in the mouse caput epididymis, epididymal fluid and spermatozoa. Meanwhile, epididymis-derived purified exosomes were isolated and validated. Subsequently, liquid chromatography tandem mass spectrometry (LC-MS) was used to perform proteomic analysis of purified exosomes. Gene Ontology (GO) analysis was performed along with pathway enrichment to identify differentially expressed proteins (DEPs).

RESULTS

Two hundred and two DEPs mostly related to endoplasmic reticulum (ER) function were identified in the exosomes separated from the epididymis of control mice and obese mice. The ER stress and CD63 (an exosome marker), both increased in the caput epididymis of obese mice. Furthermore, an in vitro study showed that palmitic acid (PA), an-oxidative stress inducer, increased exosome biogenesis and secretion in the EECs.

CONCLUSION

Oxidative stress in the epididymal microenvironment induces ER stress in the EECs. This effect alters the epididymis-derived exosome content, profile and amounts of their differentially expressed ER proteins. Such changes may affect exosome biogenesis and cargo packaging, finally leading to abnormalities in sperm maturation and fertility.

Kisspeptin Receptor on the Sperm Surface Reflects Epididymal Maturation in the Dog

Alongside the well-known central modulatory role, the Kisspeptin system, comprising Kiss1, its cleavage products (Kisspeptins), and Kisspeptin receptor (Kiss1R), was found to regulate gonadal functions in vertebrates; however, its functional role in the male gamete and its localization during maturation have been poorly understood. The present study analyzed Kisspeptin system in dog testis and spermatozoa recovered from different segments of the epididymis, with focus on Kiss1R on sperm surface alongside the maturation during epididymal transit, demonstrated by modification in sperm kinetic, morphology, and protamination. The proteins Kiss1 and Kiss1R were detected in dog testis. The receptor Kiss1R only was detected in total protein extracts from epididymis spermatozoa, whereas dot blot revealed Kiss1 immunoreactivity in the epidydimal fluid. An increase of the Kiss1R protein on sperm surface along the length of the epididymis, with spermatozoa in the tail showing plasma membrane integrity and Kiss1R protein (p < 0.05 vs. epididymis head and body) was observed by flow cytometry and further confirmed by epifluorescence microscopy and Western blot carried on sperm membrane preparations. In parallel, during the transit in the epididymis spermatozoa significantly modified their ability to move and the pattern of motility; a progressive increase in protaminization also occurred. In conclusion, Kisspeptin system was detected in dog testis and spermatozoa. Kiss1R trafficking toward plasma membrane along the length of the epididymis and Kiss1 in epididymal fluid suggested a new functional role of the Kisspeptin system in sperm maturation and storage.

Proteomic Profiling of Mouse Epididymosomes Reveals their Contributions to Post-testicular Sperm Maturation

The functional maturation of spermatozoa that is necessary to achieve fertilization occurs as these cells transit through the epididymis, a highly specialized region of the male reproductive tract. A defining feature of this maturation process is that it occurs in the complete absence of nuclear gene transcription or de novo, protein translation in the spermatozoa. Rather, it is driven by sequential interactions between spermatozoa and the complex external milieu in which they are bathed within lumen of the epididymal tubule. A feature of this dynamic microenvironment are epididymosomes, small membrane encapsulated vesicles that are secreted from the epididymal soma. Herein, we report comparative proteomic profiling of epididymosomes isolated from different segments of the mouse epididymis using multiplexed tandem mass tag (TMT) based quantification coupled with high resolution LC-MS/MS. A total of 1640 epididymosome proteins were identified and quantified via this proteomic method. Notably, this analysis revealed pronounced segment-to-segment variation in the encapsulated epididymosome proteome. Thus, 146 proteins were identified as being differentially accumulated between caput and corpus epididymosomes, and a further 344 were differentially accumulated between corpus and cauda epididymosomes (i.e., fold change of ≤ -1.5 or ≥ 1.5; p, < 0.05). Application of gene ontology annotation revealed a substantial portion of the epididymosome proteins mapped to the cellular component of extracellular exosome and to the biological processes of transport, oxidation-reduction, and metabolism. Additional annotation of the subset of epididymosome proteins that have not previously been identified in exosomes revealed enrichment of categories associated with the acquisition of sperm function (e.g., fertilization and binding to the zona pellucida). In tandem with our demonstration that epididymosomes are able to convey protein cargo to the head of maturing spermatozoa, these data emphasize the fundamental importance of epididymosomes as key elements of the epididymal microenvironment responsible for coordinating post-testicular sperm maturation.

The Effect of Dietary Supplementation of Vitamin E, Selenium, Zinc, Folic Acid, and N-3 Polyunsaturated Fatty Acids on Sperm Motility and Membrane Properties in Dogs

Sub-fertility represents a common challenge in canine reproduction. Different protocols, supplementing daily given quantities of micronutrients, were investigated to improve poor sperm concentration and/or function, which represent breeding major constraining factors in the canine species. Little information is available for dogs concerning the effect of a daily supplementation with a complex of vitamin E, zinc, selenium, folic acid, and n-3 polyunsaturated fatty acids (PUFA) on semen quality. Thus, the present study investigated this effect on semen motility and sperm membrane properties. Serial semen analyses from fourteen healthy normospermic dogs, fed with the same commercial diet, were performed on Days 0 (T0), 30 (T30), 60 (T60), and 90 (T90). Seven dogs were randomly included in the treatment (T) group, receiving a supplementation of vitamin E, zinc, selenium, folic acid, n-3 PUFA; and seven other subjects composed the control (C) group. Total Sperm Count (TSC), Computer-Assisted Sperm Analysis (CASA) indexes, mortality, and functional membrane integrity were assessed. The ANOVA compared results between groups and sampling times (p < 0.05). From T60, the supplementation significantly improved TSC, progressive motility, functional membrane integrity, and decreased mortality. Present results lead us to consider ameliorative effects of a two-month healthy diet supplementation on canine spermatozoa. The positive effects of the described balanced integration of micronutrients on sperm motility and prevention of oxidative stress should be considered, especially when decreased seminal parameters may result from inadequate intake, reduced absorption, increased losses or demand, or to attenuate the impact of age.

Effects of Estrogen Treatment on Aging in the Rat Epididymis

Previous studies from our laboratory demonstrated that estrogen signaling in the testis contributes to maintaining spermatogenesis in adult rats, and that estrogen treatment attenuated the age-associated decline in sperm production. The purpose of this study was to determine if epididymal function is also altered with age, and what effects estrogen treatment may have on the epididymis during aging. We compared untreated rats at 3 and 15 months of age to 18-month-old vehicle-treated and estrogen treated rats. In all four groups, tubule and lumen diameter of the cauda was significantly larger than more proximal regions of the epididymis. In the 3-, 15-, and 18-month-old treated animals, the epithelial cell height of the cauda was significantly shorter than that of more proximal regions. The caput cell height was shorter at 18 months compared to 3 months but this was not seen in estrogen treated animals. Thus, estrogen appears able to prevent some age related changes in epididymal morphology. Sperm transit time through the distal cauda was significantly delayed with aging. Estrogen treatment prevented this delay, indicating that sperm transit through the epididymis is an estrogen regulated function. Differences in estradiol and testosterone concentrations were observed between 3- and 15-month-old animals, but no further differences were noted between treated or untreated animals at 18 months. Interestingly, expression of androgen receptor and estrogen receptor alpha were similar between ages and treatments. Collectively, these results suggest epididymal morphology and function are affected by aging and estrogen treatment. Anat Rec, 302:1447-1457, 2019. © 2018 Wiley Periodicals, Inc.

Cellular evidence for nano-scale exosome secretion and interactions with spermatozoa in the epididymis of the Chinese soft-shelled turtle, Pelodiscus sinensis

The epididymis is the location of sperm maturation and sperm storage. Recent studies have shown that nano-scale exosomes play a vital role during these complicated processes. Our aim was to analyze the secretory properties of epididymal exosomes and their ultrastructural interaction with maturing spermatozoa in the Chinese soft-shelled turtle. The exosome marker CD63 was primarily localized to the apices of principal cells throughout the epididymal epithelium. Identification of nano-scale exosomes and their secretory processes were further investigated via transmission electron microscopy. The epithelium secreted epididymal exosomes (50~300 nm in diameter) through apocrine secretion and the multivesicular body (MVB) pathway. Spermatozoa absorbed epididymal exosomes through endocytosis or membrane fusion pathways. This study shows, for the first time, that nano-scale exosomes use two secretion and two absorption pathways in the reptile, which may be contribute to long-term sperm storage.

Identification, characterization and purification of porcine Quiescin Q6-Sulfydryl Oxidase 2 protein

Background

Post-spermiogenesis membrane surface modifications rely on molecules present in the reproductive tracts. Two isoforms (isoform 1 and 2) from Quiescin Q6-Sulfydryl Oxidase protein family have been identified in the male reproductive tract of rodent species. However, unlike isoform 1, scarce information is available for isoform 2, likely due to its lower expression level and lack of proper purification methods to obtain sufficient protein quantity for further assays.

Results

This study demonstrated the presence of short and long forms of Quiescin Q6-Sulfydryl Oxidase 2 in boar, likely representing the secretory (short form) and transmembrane (long form) forms of Quiescin Q6-Sulfydryl Oxidase 2. Immunohistochemistry studies revealed the presence of Quiescin Q6-Sulfydryl Oxidase 2 in a broad range of porcine tissues; the pronounced vesicle-contained Quiescin Q6-Sulfydryl Oxidase 2 at the apical region of epididymis and seminal vesicles epithelium suggested its involvement in sperm physiology and its participation in semen formation. The majority of porcine Quiescin Q6-Sulfydryl Oxidase 2 could be purified via either antibody affinity column or be salted out using 10%–40% ammonium sulfate. Higher amount of low molecular weight Quiescin Q6-Sulfydryl Oxidase 2 observed in the seminal vesicle likely represents the secretory form of Quiescin Q6-Sulfydryl Oxidase 2 and reflects an exuberant secretory activity in this organ.

Conclusions

We demonstrated for the first time, the presence of Quiescin Q6-Sulfydryl Oxidase 2 in porcine species; moreover, two forms of Quiescin Q6-Sulfydryl Oxidase 2 were identified and exhibited distinct molecular weights and properties during protein purification processes. This study also provided feasible Quiescin Q6-Sulfydryl Oxidase 2 purification methods from slaughterhouse materials that could potentially allow obtaining sufficient amount of Quiescin Q6-Sulfydryl Oxidase 2 for future functional investigations.

Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa

This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6) and two Vitamin E levels (200 and 400 mg kg⁻¹). During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity), and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS) extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA) and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg⁻¹) prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6) and supply of Vitamin E (400 mg kg⁻¹) successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation.

Epididymosomes: transfer of fertility-modulating proteins to the sperm surface

A variety of glycosylphosphatidylinositol (GPI)-linked proteins are acquired on spermatozoa from epididymal luminal fluids (ELF) during sperm maturation. These proteins serve roles in immunoprotection and in key steps of fertilization such as capacitation, acrosomal exocytosis and sperm-egg interactions. Their acquisition on sperm cells is mediated both by membrane vesicles (epididymosomes, EP) which were first reported to dock on the sperm surface, and by lipid carriers which facilitate the transfer of proteins associated with the membrane-free fraction of ELF. While the nonvesicular fraction is more efficient, both pathways are dependent on hydrophobic interactions between the GPI-anchor and the external lipid layer of the sperm surface. More recently proteomic and hypothesis-driven studies have shown that EP from several mammals carry transmembrane (TM) proteins, including plasma membrane Ca 2 + -ATPase 4 (PMCA4). Synthesized in the testis, PMCA4 is an essential protein and the major Ca 2 + efflux pump in murine spermatozoa. Delivery of PMCA4 to spermatozoa from bovine and mouse EP during epididymal maturation and in vitro suggests that the docking of EP on the sperm surface precedes fusion, and experimental evidence supports a fusogenic mechanism for TM proteins. Fusion is facilitated by CD9, which generates fusion-competent sites on membranes. On the basis of knowledge of PMCA4's interacting partners a number of TM and membrane-associated proteins have been identified or are predicted to be present, in the epididymosomal cargo deliverable to spermatozoa. These Ca 2 + -dependent proteins, undetected in proteomic studies, play essential roles in sperm motility and fertility, and their detection highlights the usefulness of the hypothesis-driven approach.

Reduced Fertility and Altered Epididymal and Sperm Integrity in Mice Lacking ADAM7

The mammalian epididymis is a highly convoluted tubule that connects the testis to the vas deferens. Its proper functions in sperm transport, storage, and maturation are essential for male reproduction. One of the genes predominantly expressed in the epididymis is ADAM7 (a disintegrin and metalloprotease 7). Previous studies have shown that ADAM7 synthesized in the epididymis is secreted into the epididymal lumen and is then transferred to sperm membranes, where it forms a chaperone complex that is potentially involved in sperm fertility. In this study, we generated and analyzed mice with a targeted disruption in the Adam7 gene. We found that the fertility of male mice was modestly but significantly reduced by knockout of Adam7. Histological analyses revealed that the cell heights of the epithelium were dramatically decreased in the caput of the epididymis of Adam7-null mice, suggesting a requirement for ADAM7 in maintaining the integrity of the epididymal epithelium. We found that sperm from Adam7-null mice exhibit decreased motility, tail deformation, and altered tyrosine phosphorylation, indicating that the absence of ADAM7 leads to abnormal sperm functions and morphology. Western blot analyses revealed reduced levels of integral membrane protein 2B (ITM2B) and ADAM2 in sperm from Adam7-null mice, suggesting a requirement for ADAM7 in normal expression of sperm membrane proteins involved in sperm functions. Collectively, our study demonstrates for the first time that ADAM7 is required for normal fertility and is important for the maintenance of epididymal integrity and for sperm morphology, motility, and membrane proteins.

Plasma membrane Ca2+-ATPase 4 in murine epididymis: secretion of splice variants in the luminal fluid and a role in sperm maturation

Plasma membrane Ca(2+)-ATPase isoform 4 (PMCA4) is the primary Ca(2+) efflux pump in murine sperm, where it regulates motility. In Pmca4 null sperm, motility loss results in infertility. We have shown that murine sperm PMCA4b interacts with Ca(2+)/CaM-dependent serine kinase (CASK) in regulating Ca(2+) homeostasis and motility. However, recent work indicated that the bovine PMCA4a splice variant (missing in testis) is epididymally expressed, along with 4b, and may be transferred to sperm. Here we show, via conventional and in situ RT-PCR, that both the splice variants of Pmca4 mRNA are expressed in murine testis and throughout the epididymis. Immunofluorescence localized PMCA4a to the apical membrane of the epididymal epithelium, and Western analysis not only confirmed its presence but showed for the first time that PMCA4a and PMCA4b are secreted in the epididymal luminal fluid (ELF), from which epididymosomes containing PMCA4a were isolated. Flow cytometry indicated the presence of PMCA4a on mature caudal sperm where it was increased ~5-fold compared to caput sperm (detected by Western blotting) and ~2-fold after incubation in ELF, revealing in vitro uptake and implicating PMCA4a in epididymal sperm maturation. Coimmunoprecipitation using pan-PMCA4 antibodies, revealed that both variants associate with CASK, suggesting their presence in a complex. Because they have different kinetic properties for Ca(2+) transport and different abilities to bind to CASK, our study suggests a mechanism for combining the functional attributes of both PMCA4 variants, leading to heightened efficiency of the pump in the maintenance of Ca(2+) homeostasis, which is crucial for normal motility and male fertility.

Electrophoretic Characterization of the Human Sperm-Specific Enolase at Different Stages of Maturation

The presence of a sperm-specific enolase isoform (ENO-S) in human ejaculated spermatozoa was previously demonstrated. The objective of this study was to characterize this ENO-S in spermatozoa at different steps of maturation. Sperm ENO-S was characterized in testicular, epididymal, and ejaculated spermatozoa to determine whether any change occurred in the isoform patterns of this enzyme during epididymal maturation. In testicular sperm, ENO-S was present under 2 main bands named S1 and S3. In epididymal sperm, S1 and S3 bands and a prominent additional S2 band, with the same electrophoretic properties as the S isoform of ejaculated sperm, were visualized. In the testicular extracts obtained from testes in which no spermatozoa were visualized by histologic analysis, none of the 3 ENO-S bands was found. ENO-S exists as different isoforms (electrophoretic variants) in the different stages of sperm maturation. Passage through the epididymis seems to play a major role in the maturational process of this sperm-specific enolase.

Interaction of PDC-109, the Major Secretory Protein From Bull Seminal Vesicles, With Bovine Sperm Membrane Ca2+-ATPase

PDC-109 is the prevalent secretory protein from bovine seminal vesicles that binds to the midpiece of sperm once they pass the ampulla of the vas deferens during emission. Thereby, the protein changes biophysical membrane properties, eventually resulting in increased sperm motility. To elucidate the underlying biochemical mechanism, we have studied the ion-pumping activity (Ca(2+)-ATPase) in membrane preparations of bovine spermatozoa following in vitro incubation with the protein and analyzed whether PDC-109 influences sperm motility. PDC-109 was purified to homogeneity from bull seminal vesicle extracts using a newly described method. The effect of PDC-109 on sperm motility was analyzed using the CASA-method. These experiments clearly demonstrated that PDC-109 significantly increases sperm motility. Calcium-pumping mechanisms were analyzed by monitoring the effect of PDC-109 on various parameters of enzyme activity of Ca(2+)-ATPase in epididymal sperm plasma membranes and were compared with Ca(2+)-ATPase activities from other organs and from epididymal sperm of different species, respectively. Specificity studies were performed using different Ca(2+)-antagonists. Enzyme activities of both Mg(2+)-dependent and Mg(2+)-independent Ca(2+)-ATPases increased in a dose-dependent manner following the addition of the PDC-109 (range 5-20 microg). Preincubation of PDC-109 at temperatures above 37 degrees C and pHs ranging from below 6.5 and above 8.5 led to the loss of the stimulatory effect. An analysis of enzyme kinetics pointed to irreversible, cooperative interaction of PDC-109 with the enzyme. The effect was organ-specific, that is, restricted to sperm ATPases, but it was not species-specific, as it could be elicited also in rat sperm.

Cell Specificity of Aquaporins 0, 3, and 10 Expressed in the Testis, Efferent Ducts, and Epididymis of Adult Rats

Aquaporins (AQPs) are transmembrane protein channels that allow the rapid passage of water across an epithelium at a low energy requirement, though some also transport glycerol, urea, and solutes of various sizes. At present, 11 members of the AQP family of proteins have been described in mammals, with several being localized to the testis (AQP-7 and AQP-8), efferent ducts (AQP-1 and AQP-9), and epididymis (AQP-1 and AQP-9) of adult rats. With the discovery of expression of multiple AQPs in different tissues, we undertook a systematic analysis of several other members of the AQP family on Bouin-fixed tissues of the male reproductive tract employing light microscope immunocytochemistry. In the testis, AQP-0 expression in the seminiferous epithelium was restricted to Sertoli cells and to Leydig cells of the interstitial space; no reaction was observed in the efferent ducts or epididymis. In Sertoli cells, a semicircular pattern of staining was noted, with only one fourth or one half of the Sertoli cells of a given tubule showing a reaction product. Furthermore, while Sertoli cells at stages VI-VIII of the cycle showed intense staining, those at stages IX-XIV were least reactive, with Sertoli cells at stages I-V showing intermediate levels of reaction product. The epithelial expression of AQP-10 was restricted to the microvilli of the nonciliated cells and the cilia of the ciliated cells of the efferent ducts; however, the endothelial cells of vascular channels of the efferent ducts and epididymis were also intensely reactive. AQP-3 expression was localized exclusively to the epididymis, where intense staining was noted exclusively over basal cells. Examination of orchidectomized rats revealed that AQP-3 expression was abolished over basal cells and that it was greatly diminished after efferent duct ligation. As the reaction was not fully restored in orchidectomized animals supplemented with high levels of testosterone, we suggest that AQP-3 expression in basal cells is regulated in part by testosterone, in addition to a luminal factor emanating from the testis. Together, the data indicate a cell- and tissue-specific expression for AQP-0, AQP-3, and AQP-10 in the testis, efferent ducts, and epididymis, as well as differential regulating factors for the expression of AQP-3 in basal cells.

Analysis of phosphopeptide changes as spermatozoa acquire functional competence in the epididymis demonstrates changes in the post-translational modification of Izumo1

Spermatozoa are functionally inert when they emerge from the testes. Functional competence is conferred upon these cells during a post-testicular phase of sperm maturation in the epididymis. Remarkably, this functional transformation of epididymal spermatozoa occurs in the absence of nuclear gene transcription or protein translation. To understand the cellular mechanisms underpinning epididymal maturation, we have performed a label-free, MS-based, comparative quantification of peptides from caput, corpus and caudal epididymal spermatozoa. In total, 68 phosphopeptide changes could be detected during epididymal maturation corresponding to the identification of 22 modified proteins. Included in this list are the sodium-bicarbonate cotransporter, the sperm specific serine kinase 1, AKAP4 and protein kinase A regulatory subunit. Furthermore, four phosphopeptide changes came from Izumo1, the sperm-egg fusion protein, in the cytoplasmic segment of the protein. 2D-PAGE confirmed that Izumo1 is post-translationally modified during epididymal transit. Interestingly, phosphorylation on Izumo1 was detected on residue S339 in the caput and corpus but not caudal cells. Furthermore, Izumo1 exhibited four phosphorylated residues when spermatozoa reached the cauda, which were absent from caput cells. A model is advanced suggesting that these phospho-regulations are likely to act as a scaffold for the association of adaptor proteins with Izumo1 as these cells prepare for fertilization.

The N-linked carbohydrate moiety of male reproductive tract CD52 (mrt-CD52) interferes with the complement system via binding to C1q

Antisperm antibody detected in infertile female patients' sera has been shown to correlate with reduced fertility. The antibody showed strong complement-dependent cytotoxicity as determined by the sperm immobilization test (SIT). CD52 is a human glycosylphosphatidylinositol (GPI)-anchored antigen present in lymphocytes and male reproductive tracts (mrt), including mature sperm and seminal plasma. Recently, purified mrt-CD52 from human seminal plasma has been reported to interfere with the classical complement pathway, but not lectin binding or alternative pathways of the complement system. The purpose of this study is to determine which stage of the classical pathway mrt-CD52 regulates. mrt-CD52 was purified from human seminal plasma or intact sperm membrane. Immunoprecipitation assay was performed with the reaction of mrt-CD52, human complement and mAb H6-3C4. Immunoprecipitate was formed by the carbohydrate moiety of mrt-CD52, but not by the GPI-anchor peptide. The C1q molecule (29 kDa) was detected in the immunoprecipitates by Western blotting analysis probed with anti C1q antibody, indicating that the carbohydrate moiety of mrt-CD52 binds to C1q. Also, the complement-dependent SIT revealed that purified CD52 inhibited sperm immobilization activity by antisperm antibody. These results suggest that mrt-CD52 protects sperm function from complement attack if antisperm antibody is generated in the female reproductive tracts.

Characteristics of donkey spermatozoa along the length of the epididymis

In mammals, the epididymis has numerous interrelated functions including absorptive and secretory activity that affect luminal environment and cell membrane, and the maturation and storage of sperm. Spermatozoa acquire their motility and fertilizing ability during their passage through the epididymis and the motility of epididymal spermatozoa should be a balance between the maturation of flagellum and the inhibition of the flagellar machinery. In this study maturational change in sperm characteristics were evaluated in the epididymis of donkey. Spermatozoa collected from four portions of the epididymis (head, cranial corpus, caudal corpus, tail) were compared before and after ejaculation for viability, mitochondrial activity, kinetic parameters, and morphology. A significant increase in the mitochondrial activity along the epididymis was reported, suggesting a possible involvement in the motion mechanism. This should be corroborated by the significant correlation between mitochondrial activity and the total and progressive motility and the increase in velocities of spermatozoa recorded by computer-assisted sperm analysis. The percentage of most of the abnormal spermatozoa were similar in all tracts, with a great variability between jackasses. Only the bent midpiece percentage decreased significantly along epididymis. A significant increase in the percentage of distal cytoplasmic droplets (DCD), and a simultaneous decrease in the proximal cytoplasmic droplets (PCD), was found. The DCD fell down after ejaculation suggesting the late loss of the cytoplasmic residual (DCD) in the donkey, as hypothesized in the stallion. Because the prevalence of PCD were similar in both tail epididymal and ejaculated spermatozoa, a defect of the maturative process in the PCD sperm should be speculated.

Switch of PMCA4 splice variants in bovine epididymis results in altered isoform expression during functional sperm maturation

Ca(2+) and Ca(2+)-dependent signals are essential for sperm maturation and fertilization. In mouse sperm the plasma membrane Ca(2+)-ATPase (PMCA) isoform 4 plays a crucial role in Ca(2+) transport. The two major splice variants of PMCA4 are PMCA4a and PMCA4b. PMCA4a differs from PMCA4b in the mechanism of calmodulin binding and activation. PMCA4a shows a much higher basal activity and is more effective than PMCA4b in returning Ca(2+) to resting levels. Knock-out mice carrying a PMCA4-null mutation are infertile because their sperm cannot achieve a hyperactivated state of motility. As sperm reach functional maturity during their transit through the epididymis, the expression of PMCA4a and 4b was assessed in bull testis and epididymis. Quantitative PCR revealed that PMCA4b is the major splice variant in testis, caput, and corpus epididymidis. In contrast, PMCA4a is the major splice variant in cauda epididymidis, whereas sperm are transcriptionally silent. Immunohistochemical staining using a new antibody against bovine PMCA4a located the PMCA4a to the apical membrane of the epithelium of cauda epididymidis, whereas testis, caput, and corpus epididymidis were negative. Western blotting of testis, epididymis, and sperm isolated from caput and cauda epididymidis showed a much higher level of PMCA4a in cauda epididymidis and sperm from cauda epididymidis compared with testis membranes and sperm from caput epididymidis. These findings suggest that PMCA4a is transferred to bovine sperm membranes in cauda epididymidis. This isoform switch may facilitate a higher calcium turnover in sperm necessary to traverse the female genital tract.

Integrated lipidomics in the secreted phospholipase A(2) biology

Mammalian genomes encode genes for more than 30 phospholipase A(2)s (PLA(2)s) or related enzymes, which are subdivided into several subgroups based on their structures, catalytic mechanisms, localizations and evolutionary relationships. More than one third of the PLA(2) enzymes belong to the secreted PLA(2) (sPLA(2)) family, which consists of low-molecular-weight, Ca(2+)-requiring extracellular enzymes, with a His-Asp catalytic dyad. Individual sPLA(2) isoforms exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Recent studies using transgenic and knockout mice for several sPLA(2) isoforms, in combination with lipidomics approaches, have revealed their distinct contributions to various biological events. Herein, we will describe several examples of sPLA(2)-mediated phospholipid metabolism in vivo, as revealed by integrated analysis of sPLA(2) transgenic/knockout mice and lipid mass spectrometry. Knowledge obtained from this approach greatly contributes to expanding our understanding of the sPLA(2) biology and pathophysiology.

Group III secreted phospholipase A2 regulates epididymal sperm maturation and fertility in mice

Although lipid metabolism is thought to be important for the proper maturation and function of spermatozoa, the molecular mechanisms that underlie this dynamic process in the gonads remains incompletely understood. Here, we show that group III phospholipase A2 (sPLA2-III), a member of the secreted phospholipase A2 (sPLA2) family, is expressed in the mouse proximal epididymal epithelium and that targeted disruption of the gene encoding this protein (Pla2g3) leads to defects in sperm maturation and fertility. Although testicular spermatogenesis in Pla2g3-/- mice was grossly normal, spermatozoa isolated from the cauda epididymidis displayed hypomotility, and their ability to fertilize intact eggs was markedly impaired. Transmission EM further revealed that epididymal spermatozoa in Pla2g3-/- mice had both flagella with abnormal axonemes and aberrant acrosomal structures. During epididymal transit, phosphatidylcholine in the membrane of Pla2g3+/+ sperm underwent a dramatic shift in its acyl groups from oleic, linoleic, and arachidonic acids to docosapentaenoic and docosahexaenoic acids, whereas this membrane lipid remodeling event was compromised in sperm from Pla2g3-/- mice. Moreover, the gonads of Pla2g3-/- mice contained less 12/15-lipoxygenase metabolites than did those of Pla2g3+/+ mice. Together, our results reveal a role for the atypical sPLA2 family member sPLA2-III in epididymal lipid homeostasis and indicate that its perturbation may lead to sperm dysfunction.

Epididymal hypo-osmolality induces abnormal sperm morphology and function in the estrogen receptor alpha knockout mouse

Estrogen receptor-alpha (ESR1) is highly expressed in the efferent ductules of all species studied as well as in the epididymal epithelium in mice and other select species. Male mice lacking ESR1 (Esr1KO) are infertile, but transplantation studies demonstrated that Esr1KO germ cells are capable of fertilization when placed in a wild-type reproductive tract. These results suggest that extratesticular regions, such as the efferent ductules and epididymis, are the major source of pathological changes in Esr1KO males. Previous studies have shown alterations in ion and fluid transporters in the efferent duct and epididymal epithelia of Esr1KO males, leading to misregulation of luminal fluid pH. To determine the effect of an altered epididymal milieu on Esr1KO sperm, we assayed sperm morphology in the different regions of the epididymis. Sperm recovered from the epididymis exhibited abnormal flagellar coiling and increased incidence of spontaneous acrosome reactions, both of which are consistent with exposure to abnormal epididymal fluid. Analysis of the epididymal fluid revealed that the osmolality of the Esr1KO fluid was reduced relative to wild type, consistent with prior reports of inappropriate fluid absorption from the efferent ductules. This, along with the finding that morphological defects increased with transit through the epididymal duct, suggests that the anomalies in sperm are a consequence of the abnormal luminal environment. Consistent with this, incubating Esr1KO sperm in a more wild-type-like osmotic environment significantly rescued the abnormal flagellar coiling. This work demonstrates that Esr1KO mice exhibit an abnormal fluid environment in the lumen of the efferent ducts and epididymis, precluding normal sperm maturation and instead resulting in progressive deterioration of sperm that contributes to infertility.

Immunolocalization of alpha(1A)-adrenoceptors in rat and human epididymis

Immunohistochemistry was conducted to analyze the cellular localization of alpha(1A)-adrenoceptors along rat and human epididymis. ADR-A, a polyclonal antibody that recognizes the specific C-terminal region of alpha(1A)-adrenoceptors, immunostained this adrenoceptor subtype in smooth muscle cells surrounding the epididymal tubules and interstitial blood vessels and in subpopulations of epithelial cells from adult rat and human caput and cauda epididymidis. The same cell types from rat epididymidis were immunostained by ADR-1, a polyclonal antibody that recognizes a common region of the three alpha(1)-adrenoceptor subtypes, alpha(1A), alpha(1B), and alpha(1D). Immunostaining with both antibodies was also conducted in adult rat and human vas deferens and seminal vesicle used as positive controls because of the abundance of alpha(1A)-adrenoceptors in these tissues. ADR-A- and ADR-1-positive immunostaining was differentially distributed depending on the antibody, method of tissue fixation (Bouin-fixed and fresh frozen tissues), species (rat and human), tissue (caput and cauda epididymidis), and age (immature and adult rats) analyzed. This is the first report immunolocalizing alpha(1A)-adrenoceptor along rat and human epididymis. The presence of this adrenoceptor subtype in epididymal smooth muscle and epithelial cells indicates their contribution to smooth muscle contractile responses and a possible role in the absorptive and/or secretory activities of the epithelium lining the epididymal duct. Taken together, our results should contribute to a better understanding of the physiological role of alpha(1)-adrenoceptors in the epididymidis and the importance of the sympathetic nervous system for male (in)fertility.

Identification of gene products present in Triton X-100 soluble and insoluble fractions of human spermatozoa lysates using LC-MS/MS analysis

A comprehensive analysis of the proteins found in human spermatozoa is essential for understanding the events leading up to, and including, fertilization and development. Proteomics offers a platform for investigating this process, provided that the dynamic range is relatively low. In this report, spermatozoa from a number of human sperm ejaculates were isolated in a pure state using discontinuous Percoll gradient centrifugation. Triton X-100 soluble and insoluble proteins were recovered and separated by SDS-PAGE. The separation lanes were dissected into 96 fractions and analyzed individually by LC-MS(n) . A comprehensive protocol, involving LC-MS/MS analysis eventually down to the ninth most intense peak found in the MS-survey scan, was performed. Analysis of purified human sperm populations resulted in the identification of 1056 gene products, of which approximately 8% have not previously been characterized. The data were supported by the large number of proteins represented by expressed sequence tags in the testis. Bioinformatic analysis demonstrated that 437 of the gene products were involved in various metabolic pathways including glycolysis and oxidative phosphorylation. The inventory of proteins present in the human sperm proteome includes a number of notable discoveries including the first description of a nicotinamide adenine dinucleotide phosphate oxidase, dual-oxidase 2, finally laying to rest any doubts about the presence of such enzymes in spermatozoa. Furthermore, a number of different classes of receptor have also been detected in these cells and are potential regulators of sperm function. This list includes at least six seven-pass transmembrane receptors, six tyrosine kinase receptors, a tyrosine phosphatase receptor, glutamate-gated ion channel receptors, transient receptor potential cation channels, and a non-genomic progesterone receptor. This is the first published list of identified proteins in human spermatozoa using LC-MS/MS analysis.

Genomic structure and tissue-specific expression of human and mouse genes encoding homologues of the major bovine seminal plasma proteins

Sperm capacitation is a maturation event that takes place in the female reproductive tract and is essential for fertilization. A family of phospholipid-binding proteins present in bovine seminal plasma (BSP proteins) binds the sperm membrane at ejaculation and promotes bovine sperm capacitation. Homologues of these proteins have also been isolated from boar, ram, goat, bison and stallion seminal fluid, suggesting that BSP proteins and their homologues are conserved among mammals. However, there have been no reports on BSP-homologous proteins in mice and humans to date. A search of the mouse and human genomes, using the nucleic acid sequences of BSP proteins, revealed the presence of three BSP-like sequences in the mouse genome, named mouse BSP Homologue 1 (mBSPH1), mBSPH2 and mBSPH3, and one sequence in the human genome (hBSPH1). Mouse epididymal expressed sequence tags corresponding to partial sequences of mBSPH1 and mBSPH2 were identified. The entire complementary DNA (cDNA) sequences of mBSPH1 and mBSPH2 from mouse epididymis and hBSPH1 from human epididymis were obtained by 5'-/3'-rapid amplification of cDNA ends (RACE) and encode predicted proteins containing two tandemly repeated fibronectin type II domains, which is the signature of the BSP family of proteins. Using RT-PCR, it was revealed that mBSPH1, mBSPH2 and hBSPH1 mRNA are expressed only in the epididymis. Expression of mBSPH3 was not detected in any tissue and probably represents a pseudogene. This work shows, for the first time, that BSP homologues are expressed in mouse and human and may be involved in sperm capacitation in these species.

LGR4 regulates the postnatal development and integrity of male reproductive tracts in mice

The roles of the leucine-rich repeat domain containing G protein-coupled receptor (GPCR) 4 (Lgr4), which is one of the orphan GPCRs, were analyzed with the Lgr4 hypomorphic mutant mouse line (Lgr4(Gt)). This homozygous mutant had only one-tenth the normal transcription level; furthermore, 60% of them survived to adulthood. The homozygous male was infertile, showing morphologic abnormalities in both the testes and the epididymides. In the testes, luminal swelling, loss of germinal epithelium in the seminiferous tubules, and rete testis dilation were observed. Cauda epididymidis sperm were immotile. Rete testis dilation was due to a water reabsorption failure caused by a decreased expression of an estrogen receptor (ESR1) and SLC9A3 in the efferent ducts. Although we found differential regulation of ESR1 expression in the efferent ducts and the epididymis, the role of ESR1 in the epididymis remains unclear. The epididymis contained short and dilated tubules and completely lacked its initial segment. In the caput region, we observed multilamination and distortion of the basement membranes (BMs) with an accumulation of laminin. Rupture of swollen epididymal ducts was observed, leading to an invasion of macrophages into the lumen. Male infertility was probably due to the combination of a developmental defect of the epididymis and the rupture of the epithelium resulting in the immotile spermatozoa. These results indicate that Lgr4 has pivotal roles to play in the regulation of ESR1 expression, the control of duct elongation through BM remodeling, and the regional differentiation of the caput epididymidis.

Immunolocalization of estrogen and androgen receptors and steroid concentrations in the stallion epididymis

The presence of steroids and their receptors throughout development, specifically androgen receptor (AR), estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta), in the epididymis of a high estrogen producing species like the stallion has not been determined. Epididymal and testicular samples were collected for analysis of testosterone and estradiol-17beta (E(2)) concentrations and for immunolocalization of AR, ERalpha and ERbeta. The concentration of testosterone in the testis and epididymis were not different among age groups (P>0.05). AR was localized in the principal cells of the caput, corpus and cauda in all four age groups. This lack of change in testosterone concentration and receptor localization suggests that testosterone is important for both development and maintenance of epididymal function. There was an age-related increase in E(2) concentrations in all regions of the epididymis (P<0.05), suggesting that E(2) is also important for adult function. ERbeta was localized in the principal cells of the caput, corpus and cauda in all four age groups, but the localization of ERalpha was regional and age dependent. In peri-pubertal animals, ERalpha immunostaining was most prominent and estradiol was similarly present in all three epididymal regions; this suggests that estradiol also plays a key role in the maturation of the stallion epididymis during the pubertal transition when sperm first arrive in the epididymis. In conclusion, these results suggest that the stallion epididymis is regulated by both androgens and estrogens throughout development and that estradiol is more important to epididymal function in the stallion than previously believed.

Lipid Remodeling of Murine Epididymosomes and Spermatozoa During Epididymal Maturation1

We have isolated vesicular structures from mouse epididymal fluid, referred to as epididymosomes. Epididymosomes have a roughly spherical aspect and a bilayer membrane, and they are heterogeneous in size and content. They originate from the epididymal epithelium, notably from the caput region, and are emitted in the epididymal lumen by way of apocrine secretion. We characterized their membranous lipid profiles in caput and cauda epididymidal fluid samples and found that epididymosomes were particularly rich in sphingomyelin (SM) and arachidonic acid. The proportion of SM increased markedly during epididymal transit and represented half the total phospholipids in cauda epididymidal epididymosomes. The cholesterol:phospholipid ratio increased from 0.26 in the caput to 0.48 in the cauda epididymidis. Measures of epididymosomal membrane anisotropy revealed that epididymosomes became more rigid during epididymal transit, in agreement with their lipid composition. In addition, we have characterized the membrane lipid pattern of murine epididymal spermatozoa during their maturation. Here, we have shown that mouse epididymal spermatozoa were distinguished by high percentages of SM and polyunsaturated membranous fatty acids (PUFAs), principally represented by arachidonic, docosapentanoic, and docosahexanoic acids. Both SM and PUFA increased throughout the epididymal tract. In particular, we observed a threefold rise in the ratio of docosapentanoic acid. Epididymal spermatozoa had a constant cholesterol:phospholipid ratio (average, 0.30) during epididymal transit. These data suggest that in contrast with epididymosomes, spermatozoal membranes seem to become more fluid during epididymal maturation.

New approaches for male fertility control: HE6 as an example of a putative target

Reversible contraceptive methods for males are still not available. During the last few years several marketing studies have clearly shown that men and women would welcome a situation where men could assume responsibility for family planning. Schering AG and Organon are currently collaborating to develop a hormonal method for male fertility control based on the combination of etonogestrel as gestagenic component and testosterone undecanoate. To further optimize male contraceptives in terms of improved efficiency, rapid onset, reversibility, fewer side effects and a convenient method of application, a search for innovative non-hormonal approaches was started. During the last few years, numerous proteins were identified which play a specific role in male fertility. These proteins have first to fulfil a set of indication-specific criteria before a drug discovery process can be initiated. The most important criteria for a putative target protein are tissue-selective expression, crucial biological function in fertility, drugable properties and feasibility of assay development for high-throughput-screening and lead optimization. The G-protein-coupled receptor HE6 was selected as target and the above selection criteria were applied. HE6 displays a preferred epididymis-specific expression pattern and belongs to the superfamily of GPCRs, which are well known to be drugable with small molecules. A knockout mouse was generated which revealed an infertility phenotype with the onset occurring 6 weeks after initiation of spermatogenesis at the latest. Surprisingly, no epididymis-specific phenotype was observed. Instead, the reabsorption of testicular fluid along the efferent ducts was strongly affected. No further obvious side effects were observed in male or female mice. This study with HE6 exemplifies how targets for male contraception have to be validated before drug development can start.

Expression of aquaporins in the efferent ductules, sperm counts, and sperm motility in estrogen receptor-alpha deficient mice fed lab chow versus casein

Estrogens play an important role in the male reproductive tract, and this is especially so for the efferent ductules, where alpha-estrogen receptors (ERalpha) have been localized. Mice deficient in ERalpha (alphaERKO mice) are infertile, and the effect appears to be due in part to retention of water at the level of the efferent ductules. In the present study, we examined the consequences of ERalpha deletion on the distribution of certain aquaporins (AQPs), water protein channels, in the efferent ductules and on sperm numbers and motility. In addition, the effects of feeding mice a regular lab chow diet, which contains phytoestrogens, known to affect male reproductive tract functions, and a casein diet, which lacks phytoestrogens, were also assessed. Light microscope immunolocalizations of AQP-1 and AQP-9 revealed dramatic reduction and patchier staining in alphaERKO mice with distal areas of the efferent ductules being more affected than proximal areas. No other changes in immunolocalizations were noted as a consequence of diet. Computer-assisted sperm analyses demonstrated a 62% reduction in cauda epididymal sperm/ml in alphaERKO mice fed lab chow, whereas 87% fewer sperm/ml were observed in alphaERKO mice fed casein, suggesting an enhanced role for sperm production and concentration in a diet containing phytoestrogens. All sperm motility parameters were altered to some degree in alphaERKO mice fed lab chow. Alterations in sperm motility parameters were also detected, but were less dramatic in alphaERKO mice fed casein. These data suggest that the decrease in AQP expression in the efferent ductules of alphaERKO mice contributes in part to water retention in this tissue, eventually leading to backflow of water into the testis, with subsequent decreases in sperm concentration and motility. The data also suggest that phytoestrogens, which are present in regular lab chow, can influence the male reproductive tract with and without the presence of ERalpha, promoting efferent ductule and epididymal functions when ERalpha is expressed, but inhibiting these same functions when ERalpha is missing. Taken together the data underscore the importance of estrogens and ERalpha in maintaining sperm maturation and preventing male infertility.

Expression and localization of muscarinic acetylcholine receptor subtypes in rat efferent ductules and epididymis

The expression of muscarinic acetylcholine receptor (mAChR) subtypes (M(1)-M(5)) was studied in the rat efferent ductules and epididymis at the mRNA and protein levels. The relative abundance of each mAChR transcript subtype differed depending on the tissue and the epididymal region analyzed. The M(1) mAChR mRNA level was more abundant in the efferent ductules than in the caput and cauda of the epididymis. The M(2) mAChR mRNA level was similar between the efferent ductules and caput of the epididymis and higher in the cauda region. The M(3) mAChR mRNA level was low in the efferent ductules and caput of the epididymis, but high levels were detected in the cauda region. mRNAs for M(4) and M(5) mAChRs were not detected in these tissues. Our studies indicated a variable degree of immunostaining for each mAChR subtype in a cell-type and tissue-specific pattern. M(1) mAChR was detected over the efferent ductule epithelium. M(2) and M(3) mAChRs were observed in the apical region of the ciliated cells. Apical and narrow cells of the initial segment showed distinct staining by M(1) antibody, whereas a supranuclear reaction was noted in the principal cells of the caput of the epididymis. In addition, staining for M(1) and M(2) mAChRs was visible in the apical membrane of some epithelial cells of the cauda region. M(3) mAChR was detected in the peritubular smooth muscle of the efferent ductules and epididymis. Functional studies suggested the involvement of this subtype in epididymal tubule contraction. Thus, the cell-specific expression of the various mAChR subtypes in the efferent ductules and epididymis suggests that these receptors play a role in the modulation of luminal fluid composition and smooth muscle contraction.

Effects of testosterone on muscarinic acetylcholine receptors in the rat epididymis

The effect of testosterone on the expression of muscarinic acetylcholine receptor (mAChR) subtypes was studied in the rat epididymis, at mRNA and protein level. The rat androgen status was monitored by measuring plasma testosterone level and caput and cauda epididymis wet weight. Ribonuclease protection assay (RPA) and [3H]quinuclidinyl benzilate ([3H]QNB) binding assay were performed in the caput and cauda epididymis from control (50-day old), castrated, castrated and treated with testosterone and sexually immature (30-day old) rats. The expression of each mAChR transcript subtype differed depending on the epididymal region analyzed and rat testosterone and/or testicular factors status. In control rats, RPA showed the presence of mRNA for M1, M2 and M3 mAChR in the caput and cauda epididymis. The abundance of m2 and m3 transcripts in the cauda was higher than that in the caput epididymis. Low amount of m1 transcript was observed in both regions. Orchidectomy increased m1 mRNA amount in the caput and cauda epididymis when compared to control rats, an effect slightly modified by testosterone replacement. Although orchidectomy down-regulated the level of m2 transcript in both epididymal regions, castration significantly increased m3 mRNA amount in the caput region. These effects on m2 and m3 transcripts were prevented by testosterone replacement to castrated rats. Similar abundance of m3 transcript, however, was detected in the cauda epididymis of all experimental group tested. [3H]QNB binding studies revealed that orchidectomy down-regulated the number of mAChR detected in both epididymal regions, an effect also prevented by testosterone replacement. Thus, testosterone and/or testicular factors may play a role in the regulation of mAChR expression in the rat epididymis.

Regulation of sperm function by reactive oxygen species

Sperm capacitation can be increased by the addition of reactive oxygen species (ROS) and decreased by antioxidants. Broadly consistent results have been achieved with a wide variety of methods and across different species. Exposure to ROS increases protein tyrosine phosphorylation consequent on an increase in cAMP and activation of tyrosine kinase and inhibition of tyrosine phosphatase. The measurement of ROS production by sperm is complicated by contamination of suspensions by leukocytes, laying many studies open to doubt. In human sperm the observation that extracellular NADPH could support superoxide production detected with the chemiluminescent probe lucigenin and had physiological effects similar to hydrogen peroxide led to the suggestion that they contained NADPH oxidase activity to generate ROS to support capacitation. However, the realization that lucigenin can signal superoxide artefactually, combined with failure to detect superoxide production using spin trapping techniques or to detect NADPH oxidase components in mature sperm, and confirmation of old reports that NADPH solution contains substantial amounts of hydrogen peroxide due to autoxidation, have undermined this hypothesis. Although the presence of significant NADPH oxidase activity in mature human sperm now seems less likely, other observations continue to suggest that they can make ROS in some way. There is stronger evidence that animal sperm can make ROS although these may be mainly of mitochondrial origin.

Contribution of the secretory material of caecilian (amphibia: Gymnophiona) male Mullerian gland to motility of sperm: A study inUraeotyphlus narayani

Caecilians are a unique group of limbless burrowing amphibians with discontinuous distribution. Several caecilian species are viviparous, and all practice internal fertilization. In amniotic vertebrates the sperm undergo post-testicular physiological maturation when they are initiated into motility under the influence of an epididymal secretion. Further, during ejaculation mammalian sperm are suspended in a fluid secreted by the male accessory sex glands, viz., prostate gland and seminal vesicles. Caecilians lack comparable glands, but still practice internal fertilization. Uniquely, male caecilians retain the Mullerian ducts in the adults as a pair of functional glands. It has long been hypothesized, based on indirect evidence, that the Mullerian gland would be a male accessory sex gland, secreting a fluid in which sperm are suspended during ejaculation and which would also provide nutritional support to the ejaculated sperm. In the present study, the secretory material of the Mullerian gland of Uraeotyphlus narayani was mixed with sperm obtained from the testis, and the changes in motility were recorded. Uraeotyphlus narayani sperm possess a perforatorium of the acrosome proceeding deep into the endonuclear canal of the nucleus. The midpiece is characterized by closely applied centrioles, the anterior ends of the axoneme and axial fiber, and a mitochondrial sheath. The long tail has an undulating membrane on one side, supported by the axoneme and an axial fiber. The live sperm possess a mitochondrial vesicle, also known as the cytoplasmic droplet, anywhere along the head and the midpiece, as in anuran sperm, which is shed from sperm that have ceased motility. Uraeotyphlus narayani sperm are motile the moment they are released directly from the testis, indicating that the sperm do not require post-testicular physiological maturation. On being mixed with the secretory material of the Mullerian gland, the spermatozoa are enhanced in speed as well as duration of motility. Therefore, the caecilian male Mullerian gland is considered to be the male accessory sex gland.

Analysis of reactive oxygen species generating systems in rat epididymal spermatozoa

Epididymal sperm maturation culminates in the acquisition of functional competence by testicular spermatozoa. The expression of this functional state is dependent upon a redox-regulated, cAMP-mediated signal transduction cascade that controls the tyrosine phosphorylation status of the spermatozoa during capacitation. Analysis of superoxide anion (O2(-.)) generation by rat epididymal spermatozoa has revealed a two-component process involving electron leakage from the sperm mitochondria at complexes I and II and a plasma membrane NAD(P)H oxidoreductase. Following incubation in a glucose-, lactate-, and pyruvate-free medium (-GLP), O2(-.) generation was suppressed by 86% and 96% in caput and cauda spermatozoa, respectively. The addition of lactate, malate, or succinate to spermatozoa incubated in medium -GLP stimulated O2(-.) generation. This increase could be blocked by rotenone and oligomycin (R/O) in the presence of malate or lactate but not succinate. Stimulation with all three substrates, as well as spontaneous O2(-.) production in +GLP medium, was blocked by the flavoprotein inhibitor, diphenylene iodonium. Diphenylene iodonium, but not R/O, suppressed NAD(P)H-induced lucigenin-dependent chemiluminescence. This NAD(P)H-dependent enzyme resided in the sperm plasma membrane and its activity was regulated by zinc and uncharacterized cytosolic factors. Reverse transcription-polymerase chain reaction analysis indicated that the sperm NAD(P)H oxidoreductase complex is quite distinct from the equivalent leukocyte system.

Cloning and sequencing of human Eppin: a novel family of protease inhibitors expressed in the epididymis and testis

In this report we describe the discovery of Eppin (Epididymal protease inhibitor), a gene on human chromosome 20 expressing three mRNAs encoding two isoforms of a cystine-rich protein containing both Kunitz-type and WAP-type four disuffide core protease inhibitor consensus sequences. Analysis of Eppin's genomic sequence from chromosome 20q12-13.2 predicts the existence of all three splice variants of Eppin and that all the exons conform to the AG/GT splicing rule. The presence of single bands on a Southern blot of human genomic DNA suggests that Eppin is a single copy gene. TATA box transcription initiation sites are present for both of the different Eppin 5' UTRs and examination of the promoter region 1800 bp upstream of the start codon revealed a number of putative transcription enhancer binding sites typical of genes expressed in the epididymis or testis. Northern blot and tissue specific PCR data indicate Eppin-1 is expressed only in the testis and epididymis; Eppin-2 is expressed only in the epididymis and Eppin-3 only in the testis. Antiserum prepared against recombinant EPPIN recognizes several strong bands on Western blots of human epididymal extracts from the caput and corpus regions. Immunohistochemistry indicates a strong pattern of expression by the ciliated cells of the efferent ducts and strong staining of ejaculated spermatozoa. Eppin represents the first member of a family of protease inhibitors characterized by dual inhibitor consensus sequences, both WAP-type and Kunitz-type consensus sequences. A second family member is predicted to exist on chromosome 20 approximately 4 kb downstream from Eppin's exon I, which has two WAP-type sequences and one Kumtz-type consensus sequence.

Antisperm antibodies associated with infertility: properties and encoding genes of target antigens

Infertility among couples of reproductive age is a perplexing condition when the cause is indeterminate. These cases are classified as unexplained infertility. In a subset of subjects, antisperm antibodies with sperm agglutinating and/or immobilizing activities have been detected in the blood or fluids of the reproductive tract. These cases are designated as immunologic infertility although a cause and effect relationship of the antibodies to infertility has not been established. In this review, seven target sperm antigens to antibodies associated with infertility and their encoding genes are described. The antisperm antibodies (ASAs) examined were obtained from infertile women or were monoclonal antibodies (mAb) raised against human sperm proteins. All the ASAs studied possessed potent sperm agglutinating and/or immobilizing activities. The target antigens were isolated from human and other mammalian sperm, and the encoding genes identified. The seven antigens are YWK-II, BE-20, rSMP-B, BS-63 (nucleoporin-related), BS-17 (calpastatin), HED-2 (zyxin), and 75- kDa. Each antigen is a distinct and separate entity and is produced by different cells of the reproductive tract, (e.g., germ cells, epididymal epithelial cells, and Sertoli cells). No single predominant target component has been found to interact with the ASAs. It is proposed that immunologic infertility is the consequence of the combined actions of multiple ASAs in immobilizing and/or agglutinating spermatozoa, blocking spermegg interaction, preventing implantation, and/or arresting embryo development.

The c-ros tyrosine kinase receptor controls regionalization and differentiation of epithelial cells in the epididymis

The c-ros gene was originally identified in mutant form as an oncogene. The proto-oncogene encodes a tyrosine kinase receptor that is expressed in a small number of epithelial cell types, including those of the epididymis. Targeted mutations of c-ros in the mouse reveal an essential role of the gene in male fertility. Male c-ros -/- animals do not reproduce, whereas the fertility of female animals is not affected. We demonstrate that c-ros is not required in a cell autonomous manner for male germ cell development or function. The gene, therefore, does not affect sperm generation or function in a direct manner. The primary defect in the mutant animals was located in the epididymis, showing that c-ros controls appropriate development of the epithelia, particularly regionalization and terminal differentiation. The epididymal defect does not interfere with production or storage of sperm but, rather, with sperm maturation and the ability of sperm to fertilize in vivo. Interestingly, sperm isolated from c-ros -/- animals can fertilize in vitro. Our results highlight the essential role of the epididymis in male fertility and demonstrate a highly specific function of the c-ros receptor tyrosine kinase during development of distinct epithelial cells.