Stallion epididymal fluid proteome: qualitative and quantitative characterization; secretion and dynamic changes of major proteins

Proteomics is advancing the understanding of stallion sperm biology

The mammalian ejaculate is very well suited to proteomics studies. As such, research concerning sperm proteomics is offering a huge amount of new information on the biology of spermatozoa. Among domestic animals, horses represent a species of special interest, in which reproductive technologies and a sizeable market of genetic material have grown exponentially in the last decade. Studies using proteomic approaches have been conducted in recent years, showing that proteomics is a potent tool to dig into the biology of the stallion spermatozoa. The aim of this review is to present an overview of the research conducted, and how these studies have improved our knowledge of stallion sperm biology. The main outcomes of the research conducted so far have been an improved knowledge of metabolism, and its importance in sperm functions, the impact of different technologies on the sperm proteome, and the identification of potential biomarkers. Moreover, proteomics of seminal plasma and phosphoproteomics are identified as areas of major interest.

The significance of single-cell transcriptome analysis in epididymis research

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

Proteome Profiling of Canine Epididymal Fluid: In Search of Protein Markers of Epididymal Sperm Motility

Sperm maturation in the epididymis is based on interactions with proteins from epididymal fluid (EF). The aim of the study was to profile canine EF proteome and investigate correlations between EF protein content and epididymal spermatozoa (ES) motion parameters. Twenty-three male dogs were divided into two groups: good sperm motility (GSM) and poor sperm motility (PSM). The total motility and progressive motility differed significantly (p = 0.031; p < 0.001, respectively) between the GSM group and the PSM group. The semen samples were centrifuged to separate the EF apart from the ES. The canine EF proteins were analyzed using nano-liquid chromatography, which was coupled with quadrupole time-of-flight mass spectrometry (NanoUPLC-Q-TOF/MS) and bioinformatic tools for the first time. A total of 915 proteins were identified (GSM-506; PSM-409, respectively). UniProt identification resulted in six unique proteins (UPs) in the GSM group of dogs and four UPs in the PSM group. A semi-quantitative analysis showed a higher abundance (p < 0.05) of four differentially expressed proteins in the GSM group (ALB, CRISP2, LCNL1, PTGDS). Motility-dependent variations were detected in the EF proteome and were related to important metabolic pathways, which might suggest that several proteins could be potential ES motility biomarkers.

The stallion sperm acrosome: Considerations from a research and clinical perspective

During the fertilization process, the interaction between the sperm and the oocyte is mediated by a process known as acrosomal exocytosis (AE). Although the role of the sperm acrosome on fertilization has been studied extensively over the last 70 years, little is known about the molecular mechanisms that govern acrosomal function, particularly in species other than mice or humans. Even though subfertility due to acrosomal dysfunction is less common in large animals than in humans, the evaluation of sperm acrosomal function should be considered not only as a complementary but a routine test when individuals are selected for breeding potential. This certainly holds true for stallions, which might display lower levels of fertility in the face of "acceptable" sperm quality parameters determined by conventional sperm assays. Nowadays, the use of high throughput technologies such as flow cytometry or mass spectrometry-based proteomic analysis is commonplace in the research arena. Such techniques can also be implemented in clinical scenarios of males with "idiopathic" subfertility. The current review focuses on the sperm acrosome, with particular emphasis on the stallion. We aim to describe the physiological events that lead to the acrosome formation within the testis, the role of very specific acrosomal proteins during AE, the methods to study the occurrence of AE under in vitro conditions, and the potential use of molecular biology techniques to discover new markers of acrosomal function and subfertility associated with acrosomal dysfunction in stallions.

Proteomics Evaluation of Semen of Clinically Healthy Beagle-Breed Dogs

The objectives of the present work were to evaluate the semen of dogs by means of proteomics methods and to compare with proteomics results of the blood of the animals, in order to increase available knowledge on the topic and present relevant reference values for semen samples. Semen samples were collected from five Beagle-breed dogs. Reproductive assessment of the animals by means of clinical, ultrasonographic and seminological examinations confirmed their reproductive health. The sperm-rich fraction and the prostatic fraction of semen were processed for proteomics evaluation. LC-MS/MS analysis was performed by means of a LTQ Orbitrap Elite system. The technology combines high separation capacity and strong qualitative ability of proteins in biological samples that require deep proteome coverage. Protein classification was performed based on their functional annotations using Gene Ontology (GO). In blood plasma, semen sperm-rich fraction, and semen prostatic fraction, 59, 42 and 43 proteins, respectively, were detected. Two proteins were identified simultaneously in plasma and the semen sperm-rich fraction, 11 proteins in plasma and the semen prostatic fraction, and three proteins in the semen sperm-rich and prostatic fractions. In semen samples, most proteins were related to cell organization and biogenesis, metabolic processes or transport of ions and molecules. Most proteins were located in the cell membrane, the cytosol or the nucleus. Finally, most proteins performed functions related to binding or enzyme regulation. There were no differences between the semen sperm-rich fraction and prostatic fractions in terms of the clustering of proteins. In conclusion, a baseline reference for proteins in the semen of Beagle-breed dogs is provided. These proteins are involved mostly in supporting spermatozoan maturation, survival and motility, enhancing the reproductive performance of male animals. There appears potential for the proteomics examination of semen to become a tool in semen evaluation. This analysis may potentially identify biomarkers for reproductive disorders. This can be particularly useful in stud animals, also given its advantage as a non-invasive method.

Age-Dependent Variations in Functional Quality and Proteomic Characteristics of Canine (Canis lupus familiaris) Epididymal Spermatozoa

Increased male age is associated with a significant reduction in semen quality. Little is known about the sperm proteome changes resulting from the aging process. This study aimed to investigate the relationship between the functional quality and proteome of epididymal spermatozoa of dogs that were differing in age. The study was conducted on 30 male dogs that were divided into three age groups. G1—12 to 41 months old, G2—42 to 77 months old, and G3—78 to 132 months old. The sperm samples were assessed using a computer-assisted semen analysis (CASA). The epididymal sperm proteins were analyzed using gel electrophoresis (SDS-PAGE), nano-liquid chromatography coupled to quadrupole time of flight mass spectrometry (NanoUPLC-Q-TOF/MS) and bioinformatic tools. The sperm quality parameters were significantly lower in older dogs. NanoUPLC-Q-TOF/MS identification resulted in 865 proteins that were found in the G1, 472 in G2, and 435 in G3. There were seven proteins that were present in all three age groups, and four of them (ACTB, CE10, NPC2, CRISP2) showed significant changes among the studied groups. Age-dependent variations were detected in the sperm proteome composition and were related to important metabolite pathways, which might suggest that several proteins are implicated in sperm maturation and could be potential aging biomarkers.

Zinc-binding proteins in stallion seminal plasma as potential sperm function regulators

Sperm functions may be influenced by seminal plasma (SP) proteins with affinity to zinc ions. The aim of the study was to isolate and characterise zinc-binding proteins (ZnBPs) from stallion SP using proteomic tools. Zinc-binding proteins were isolated from the SP of eight stallions by zinc-affinity chromatography. They were analysed in the SDS-PAGE system, and peptide extracts were prepared. Samples of ZnBPs isolated from stallion SP were injected onto the nLC-1000 nanoflow HPLC system coupled via a nano-electrospray ion source to the Orbitrap Elite FTMS mass spectrometer (Thermo Fisher Scientific). Raw MS data were analysed using MaxQuant software with label-free quantification (LFQ). Protein sequences were obtained from the UniProt database. Forty-seven proteins in ZnBPs were annotated in a gene ontology (GO) analysis. The LFQ intensity analysis of individual proteins revealed that ZnBPs comprised mainly clusterin (CLU, 27%), serin protease inhibitor F1 (SERPINF1, 13%), actin, cytoplasmic 1 (ACTB, 9%), nucleobindin 2 (NUCB2, 8%) and polymeric immunoglobulin receptor (PIGR, 6%). This is the first proteomic study to analyse ZnBPs in stallion SP. The present findings show that ZnBPs in stallion SP could play an important role in the regulation of sperm function.

The Knowns and Unknowns about Epididymal Extracellular Vesicles in Different Animal Species

Sperm maturation during epididymal transit is a long and complex process. Although the roles of epididymal extracellular vesicles (EVs) on sperm quality have been extensively studied in recent years, there are still a lot of unexplored areas and too few species that are studied. The objective of this review is to focus on the contribution of epididymal EVs through the apocrine secretion of key factors, including proteins and small RNAs. Furthermore, the authors explore the alterations in the content of these vesicles related to male fertility and the effects of environmental stressors, and how these factors vary across taxa. Last, potential applications are covered, and the next steps in that field of research are highlighted.

Fractionated Seminal Plasma of Boar Ejaculates Analyzed by LC-MS/MS: Its Effects on Post-Thaw Semen Quality

This study aimed to characterize the protein composition of fractionated seminal plasma (SP) by liquid chromatography mass spectrometry (LC–MS/MS) analysis and investigate its effects on survival of frozen-thaw (FT) boar spermatozoa following storage. Seminal plasma (SP) was fractionated by gel filtration chromatography to give two fractions, SP1 with more than 40 kDa (>40 kDa) and SP2 with less than 40 kDa (<40 kDa). SP1 and SP2 were subjected to LC–MS/MS and bioinformatics analysis. Following cryopreservation, FT boar semen (n = 7) was thawed in Beltsville Thawing Solution (BTS), BTS + SP1 or BTS + SP2, stored at different periods and subjected to post-thaw (PT) quality assessment. A total of 52 and 22 abundant proteins were detected in SP1 and SP2, respectively. FN1, ANGPTL1, and KIF15 proteins were more abundance in SP1, whereas a high abundance of spermadhesins (PSP-I and PSP-II) was detected in SP2. Proteins of the fractionated SP were involved in various biological processes, such as cell motility and signal transduction. The dominant pathway of SP1 proteins was the apelin signaling pathway (GNA13, MEF2D, SPHK2, and MEF2C), whereas a pathway related to lysosome (CTSH, CTSB, and NPC2) was mainly represented by SP2 proteins. In most of the boars, significantly higher motility characteristics, membrane integrity, and viability were observed in FT spermatozoa exposed to SP1 or SP2 compared with BTS. The results of our study confirm that a combination of several proteins from the fractionated SP exerted beneficial effects on the sperm membrane, resulting in improved quality characteristics following PT storage.

Castration causes an increase in lysosomal size and upregulation of cathepsin D expression in principal cells along with increased secretion of procathepsin D and prosaposin oligomers in adult rat epididymis

In the epididymis, lysosomal proteins of the epithelial cells are normally targeted from the Golgi apparatus to lysosomes for degradation, although their secretion into the epididymal lumen has been documented and associated with sperm maturation. In this study, cathepsin D (CatD) and prosaposin (PSAP) were examined in adult epididymis of control, and 2-day castrated rats without (Ct) and with testosterone replacement (Ct+T) to evaluate their expression and regulation within epididymal epithelial cells. By light microscope-immunocytochemistry, a quantitative increase in size of lysosomes in principal cells of Ct animals was noted from the distal initial segment to the proximal cauda. Androgen replacement did not restore the size of lysosomes to control levels. Western blot analysis revealed a significant increase in CatD expression in the epididymis of Ct animals, which suggested an upregulation of its expression in principal cells; androgens restored levels of CatD to that of controls. In contrast, PSAP expression in Ct animals was not altered from controls. Additionally, an increase in procathepsin D levels was noted from samples of the epididymal fluid of Ct compared to control animals, accompanied by an increased complex formation with PSAP. Moreover, an increased oligomerization of prosaposin was observed in the epididymal lumen of Ct rats, with changes reverted to controls in Ct+T animals. Taken together these data suggest castration causes an increased uptake of substrates that are acted upon by CatD in lysosomes of principal cells and in the lumen by procathepsin D. These substrates may be derived from apoptotic cells noted in the lumen of proximal regions and possibly by degenerating sperm in distal regions of the epididymis of Ct animals. Exploring the mechanisms by which lysosomal enzymes are synthesized and secreted by the epididymis may help resolve some of the issues originating from epididymal dysfunctions with relevance to sperm maturation.

Effects of exogenous lactoferrin on characteristics and functions of bovine epididymal, ejaculated and frozen-thawed sperm

The purpose of this study was to investigate effects of addition of lactoferrin on characteristics and functions of bovine epididymal, ejaculated, and frozen-thawed sperm. The addition of lactoferrin was significantly (p < .05) effective on increasing values of progressive motility, straightness, and linearity in caput epididymal sperm and values of motility in cauda epididymal sperm. When ejaculated sperm were incubated in capacitation medium, percentages of motile and progressively motile sperm decreased largely within the first period of 30 min, followed by only minor changes. However, the addition of lactoferrin significantly lessened the early decreases of these parameters and additionally promoted capacitation-dependent changes of chlortetracycline staining patterns (from F pattern to B pattern). In other experiments, when ejaculated sperm were exposed to oxidative stress with 100-µM H₂ O₂ , the addition of lactoferrin partially protected them from dysfunction of flagellar movement and loss of progressive movement. In final experiments with frozen-thawed samples incubated in the capacitation medium, the addition of lactoferrin effectively survived dying sperm and suppressed occurrence of sperm agglutination. These results may suggest biological and biotechnological potentials of lactoferrin for modulation of bovine sperm viability, motility, capacitation state, and preservation in vitro.

Transcriptome analysis of turkey (Meleagris gallopavo) reproductive tract revealed key pathways regulating spermatogenesis and post-testicular sperm maturation

The application of transcriptomics to the study of the reproductive tract in male turkeys can significantly increase our current knowledge regarding the specifics of bird reproduction. To characterize the complex transcriptomic changes that occur in the testis, epididymis, and ductus deferens, deep sequencing of male turkey RNA samples (n = 6) was performed, using Illumina RNA-Seq. The obtained sequence reads were mapped to the turkey genome, and relative expression values were calculated to analyze differentially expressed genes (DEGs). Statistical analysis revealed 1,682; 2,150; and 340 DEGs in testis/epididymis, testis/ductus deferens, and epididymis/ductus deferens comparisons, respectively. The expression of selected genes was validated using quantitative real-time reverse transcriptase-polymerase chain reaction. Bioinformatics analysis revealed several potential candidate genes involved in spermatogenesis, spermiogenesis and flagellum formation in the testis, and in post-testicular sperm maturation in the epididymis and ductus deferens. In the testis, genes were linked with the mitotic proliferation of spermatogonia and the meiotic division of spermatocytes. Histone ubiquitination and protamine phosphorylation were shown to be regulatory mechanisms for nuclear condensation during spermiogenesis. The characterization of testicular transcripts allowed a better understanding of acrosome formation and development and flagellum formation, including axoneme structures and functions. Spermatozoa motility during post-testicular maturation was linked to the development of flagellar actin filaments and biochemical processes, including Ca2+ influx and protein phosphorylation/dephosphorylation. Spermatozoa quality appeared to be controlled by apoptosis and antioxidant systems in the epididymis and ductus deferens. Finally, genes associated with reproductive system development and morphogenesis were identified. To the best of our knowledge, this is the first genome-wide functional investigation of genes associated with tissue-specific processes in turkey reproductive tract. A catalog of genes worthy of further studies to understand the avian reproductive physiology and regulation was provided.

Interplay between male reproductive system dysfunction and the therapeutic effect of flavonoids

Male infertility has affected many families around the world. However, due to the mechanism underlying male reproductive system dysfunction are not completely elucidated, the use of drugs for male reproductive system dysfunction treatment only insignificant higher pregnancy outcomes, low-quality evidence suggests that clinical pregnancy rates may increase. Therefore, the focus in the future will be on developing more viable treatment options to prevent or treatment of male reproductive system dysfunction and achieve the purpose of improving fertility. Interestingly, natural products, as the potential inhibitors for the treatment of male reproductive system dysfunction, have shown a good therapeutic effect. Among many natural products, flavonoids have been extensively investigated for the treatment of male reproductive system dysfunction, such as testicular structural disruption, spermatogenesis disturbance and sperm quality decline. Flavonoids have been reported to have antioxidant, anti-inflammatory, immune stimulating, anti-apoptotic, anticarcinogenic, anti-allergic and antiviral activities, investigating for the treatment of male reproductive system dysfunction. In this review, we evaluate the therapeutic effects of flavonoids on male reproductive system dysfunction under different cellular scenarios and summarize the therapeutic strategies of flavonoids based on the aforementioned retrospective analysis. In the end, we describe some perspective research areas relevant to the application of flavonoids in the treatment of male reproductive system dysfunction.

Retrograde flushing collection and freezing of dromedary camel epididymal spermatozoa with seminal plasma

The objectives of this study were to describe the parameters of dromedary camel epididymal spermatozoa collected by retrograde flushing (RF) technique and to evaluate the freezability of the collected sperm, diluted with and without the supplementation of seminal plasma (SP). Two experiments were conducted: in Experiment 1, ES were recovered within 6-8 h after castration; selected samples were diluted with a Tris-citrate egg-yolk glycerolated buffer and frozen. In Experiment 2, epididymides were stored for 24 h at 4 °C before RF and semen samples were frozen after dilution with a Tris-lactose egg-yolk glycerolated extender with and without 15% SP. In Experiment 1, eight semen samples were obtained from ten epididymides with a mean of 500 × 106 total spermatozoa recovered, per flushed epididymis. Mean post-thaw motility and progressive motility were 75 and 17%, respectively. In Experiment 2, 15 samples were collected, out of the 18 epididymides (mean number of collected spermatozoa: 700 × 106), and 13 of these samples were of excellent quality. Post-thaw parameters were not satisfactory but the supplementation of the freezing medium with 15% SP improved the progressive motility and kinematic parameters of the spermatozoa.

Seminal plasma AnnexinA2 protein is a relevant biomarker for stallions which require removal of seminal plasma for sperm survival upon refrigeration†

Some stallions yield ejaculates that do not tolerate conservation by refrigeration prior to artificial insemination (AI), showing improvement after removal of most of the seminal plasma (SP) by centrifugation. In this study, the SP-proteome of 10 different stallions was defined through high-performance liquid chromatography with tandem mass spectrometry and bioinformatic analysis in relation to the ability of the ejaculates to maintain semen quality when cooled and stored at 5°C. Stallions were classified into three groups, depending on this ability: those maintaining good quality after direct extension in a commercial extender (good), stallions requiring removal of seminal plasma (RSP) to maintain seminal quality (good-RSP), and stallions, unable to maintain good semen quality even after RSP (poor). Pathway enrichment analysis of the proteins identified in whole equine SP using human orthologs was performed using g: profiler showing enriched Reactome and the Kyoto Encyclopedia of Genes and Genomes pathways related to hexose metabolism, vesicle mediated transport, post translational modification of proteins and immune response. Specific proteins overrepresented in stallions tolerating conservation by refrigeration included a peroxiredoxin-6 like protein, and transcobalamin-2, a primary vitamin B12-binding, and transport protein. Also, the protein involved in protein glycosylation, ST3 beta-galactoside alpha-2,3-sialyltransferase 1 was present in good stallions. These proteins were nearly absent in poor stallions. Particularly, annexinA2 appeared as to be the most powerful discriminant variable for identification of stallions needing RSP prior to refrigeration, with a P = 0.002 and a q value = 0.005. Overall this is the first detailed study of the equine SP-proteome, showing the potential value of specific proteins as discriminant bio-markers for clinical classification of stallions for AI.

Epididymal contribution to male infertility: An overlooked problem

The diagnosis and treatment of male infertility, excluding assisted conception, are limited because of, but not limited to, poor understanding of sperm post-testicular development and storage. Many may think that sperm dysfunction is only self-contained in the sperm cell itself as a result of defective spermatogenesis. However, it can also be a consequence of inadequate epididymal maturation following disorders of the epididymis. Improper epididymal functions can disturb semen parameters and sperm DNA integrity, result in high leucocyte concentrations and high numbers of immature germ cells and debris or even cause idiopathic infertility. To date, the data are limited regarding critical markers of sperm maturation and studies that can identify such markers for diagnosis and managing epididymal dysfunction are scarce. Therefore, this article aims to draw attention to recognise a disturbed epididymal environment as a potential cause of male infertility.

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

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

Equine seminal plasma and sperm membrane: Functional proteomic assessment

During ejaculation, a large amount of seminal plasma proteins interact with the sperm membrane, leading to a series of biochemical and structural changes implicated in sperm function and gamete interaction. However, the roles of the majority of these proteins remain unknown. This study aimed to investigate the proteome and functionality of the major equine proteins of seminal plasma and the sperm membrane. Seminal plasma and enriched-membrane proteins (150 μg) were separated by two-dimensional gel electrophoresis, and the respective maps were analyzed. Protein identification was performed by in-gel digestion and tandem mass spectrometry (GeLC-MS/MS). Samples were also submitted to in-solution digestion (complex protein mixture) and identified by shotgun analysis by LC-MS/MS; bioinformatic tools were used to investigate protein functions. Seminal plasma and sperm membrane extract maps contained 91.0 ± 8.2 spots and 245.3 ± 11.3 spots, respectively, within the 3-10 pH range. In total, the most abundant proteins identified in 2D maps and in complex protein mixtures included 24 proteins for seminal plasma and 33 for sperm membrane extract, with a high degree of confidence (P < 0.05). Of these, HSP1, CRISP3 and KLK1E2 were the most abundant in seminal plasma; HSP1 was highly abundant in sperm membrane extract, in many isoforms, which is related to membrane destabilization and may compromise sperm preservation. HSP1-polybromo-1 interactions suggested a role in DNA stabilization. Prosaposin was identified in seminal plasma and may play a role in the fertilization process. IZUMO4, a member of the IgSF family involved in the prefertilization stages, was identified in 2D gel and MS/MS analysis of sperm membrane extract. Ten proteins of seminal plasma were found to interact with the sperm membrane and were related to binding and catalytic activities (clusterin, CRISP3, epididymal sperm-binding protein 1, kallikrein1E2, seminal plasma protein A3, and HSP1). Additionally, other identified proteins were associated with DNA integrity, capacitation and recognition of pregnancy. These findings indicate that the binding of specific proteins to the plasma membrane during ejaculation may influence sperm survival after cryopreservation and may play a role in decreasing the quality in stallions with toxic seminal plasma. Elucidation of these interactions is an important step in understanding the biological processes related to equine fertility and facilitates future investigations on the selection and application of low freezability semen strategies.

Comparative RNA-Seq Analysis of Differentially Expressed Genes in the Epididymides of Yak and Cattleyak

Background

Cattleyak are the Fl hybrids between (♀) yak (Bos grunniens) and (♂) cattle (Bos taurus). Cattleyak exhibit higher capability in adaptability to a harsh environment and display much higher performances in production than the yak and cattle. The cattleyak, however, are females fertile but males sterile. All previous studies greatly focused on testes tissues to study the mechanism of male infer-tility in cattleyak. However, so far, no transcriptomic study has been conducted on the epididymides of yak and cattleyak.

Objective

Our objective was to perform comparative transcriptome analysis between the epididymides of yak and cattleyak and predict the etiology of male infertility in cattleyak.Methods: We performed comparative transcriptome profiles analysis by mRNA sequencing in the epidi-dymides of yak and cattleyak.

Results

In total 3008 differentially expressed genes (DEGs) were identified in cattleyak, out of which 1645 DEGs were up-regulated and 1363 DEGs were down-regulated. Thirteen DEGs were validated by quantitative real-time PCR. DEGs included certain genes that were associated with spermatozoal matura-tion, motility, male fertility, water and ion channels, and beta-defensins. LCN9, SPINT4, CES5A, CD52, CST11, SERPINA1, CTSK, FABP4, CCR5, GRIA2, ENTPD3, LOC523530 and DEFB129, DEFB128, DEFB127, DEFB126, DEFB124, DEFB122A, DEFB122, DEFB119 were all downregu-lated, whereas NRIP1 and TMEM212 among top 30 DEGs were upregulated. Furthermore, protein processing in endoplasmic reticulum pathway was ranked at top-listed three significantly enriched KEGG pathways that as a consequence of abnormal expression of ER-associated genes in the entire ER protein processing pathway might have been disrupted in male cattleyak which resulted in the down-regulation of several important genes. All the DEGs enriched in this pathway were downregulated ex-cept NEF.

Conclusion

Taken together, our findings revealed that there were marked differences in the epididymal transcriptomic profiles of yak and cattleyak. The DEGs were involved in spermatozoal maturation, mo-tility, male fertility, water and ion channels, and beta-defensins. Abnormal expression of ER-associated genes in the entire ER protein processing pathway may have disrupted protein processing pathway in male cattleyak resulting in the downregulation of several important genes involved in sperm maturation, motility and defense.

Mouse quiescin sulfhydryl oxidases exhibit distinct epididymal luminal distribution with segment-specific sperm surface associations

Sulfhydryl oxidation is part of the sperm maturation process essential for the acquisition of sperm fertilization competency and its structural stabilization; however, the specific sulfhydryl oxidases that fulfill these roles have yet to be identified. In this study, we investigate the potential involvement of one atypical thiol oxidase family called quiescin Q6/sulfhydryl oxidase (QSOX) using the mouse epididymis as our model system. With multidisciplinary approaches, we show that QSOX isoform 1 and 2 exhibit complementary distribution throughout the epididymal duct, but that each variant possesses distinct subcellular localization within the epididymal principal cells. While QSOX2 was exclusively present in the Golgi apparatus of the caput and corpus epididymis, QSOX1c, the most profusely express QSOX1 variant, was abundantly present in the cauda luminal fluids. Moreover, immunohistochemistry studies together with proteomic identification in isolated epididymosomes provided evidence substantiating the release of QSOX2, but not QSOX1c, via an apocrine secretory pathway. Furthermore, we demonstrate for the first time, distinct association of QSOX1c and QSOX2 with the sperm acrosome and implantation fossa, during different stages of their epididymal maturation. In conclusion, our study provides the first comprehensive comparisons between QSOX1 and QSOX2 in the mouse epididymis, revealing their distinct epididymal distribution, cellular localization, mechanisms of secretion and sperm membrane association. Together, these data suggest that QSOX1 and QSOX2 have discrete biological functions in male germ cell development.

The expression of the new epididymal luminal protein of PDZ domain containing 1 is decreased in asthenozoospermia

Spermatozoa are not mature until they transit the epididymis where they acquire motility and the ability to fertilize an egg through sequential modifications. The epididymis has three functional regions, caput, corpus, and cauda, and the luminal proteins of the epididymis play important roles in the above modifications. However, the proteins with differential enrichment between the caput and cauda are still largely unknown. To reveal the functions of the caput and cauda during sperm maturation, luminal proteins from caput and cauda of mice were analyzed by isobaric tag for relative and absolute quantitation (iTRAQ). Overall, 128 differentially enriched proteins were found, of which 46 were caput enriched and 82 were cauda enriched. Bioinformatic analysis showed that lipid metabolism was active in the caput; while anion- and cation-binding activity and phosphorus and organophosphate metabolism were active in the cauda. A new epididymal luminal protein, the caput-enriched PDZ domain containing 1 (Pdzk1), also named Na⁺/H⁺ exchange regulatory cofactor 3 (NHERF3), which plays a critical role in cholesterol metabolism and carnitine transport, was found in the lipid metabolism. Western blotting and immunofluorescence analyses showed that Pdzk1 was expressed in the epididymis but not in the testis, and localized at the middle piece of the sperm tail. Pdzk1 protein level was also reduced in the spermatozoa in case of asthenozoospermic patients compared with that in normozoospermic men, suggesting that Pdzk1 may participate in sperm maturation regulation and may be associated with male infertility. These results may provide new insights into the mechanisms of sperm maturation and male infertility.

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.

Effect of Cistanche Tubulosa Extracts on Male Reproductive Function in Streptozotocin⁻Nicotinamide-Induced Diabetic Rats

Diabetes is a chronic disorder characterized by hyperglycemia due to decreased levels of insulin or the inefficiency of the tissue to use it effectively. Infertility is known as a major outcome of diabetes and affects the male reproductive system by causing sperm impairment and gonadal dysfunction. Cistanche tubulosa is a parasitic plant which has the capacity to improve memory, immunity, and sexual ability, reduce impotence, and minimize constipation. This study was focused on the investigation of the anti-inflammatory and protective effects of echinacoside (ECH) in Cistanche tubulosa extract (CTE) on the male reproductive system of the diabetic rats. The antioxidant, anti-inflammatory, and protective effects of CTE were evaluated by both in vitro and in vivo methods. The in vitro results show that the ECH inhibited reactive oxygen species (ROS) production and improved StAR, CYP11A1, CYP17A1, and HSD17β3 protein expression. The in vivo analysis was carried out with three doses of echinacoside (ECH) (80, 160, and 320 mg/kg) in CTE. In total, 0.571 mg/kg of rosiglitazone (RSG) was administered as a positive control. Diabetes was induced by streptozotocin (STZ) (65 mg/kg) and nicotinamide (230 mg/kg) in combination with a high-fat diet (45%). The in vivo studies confirmed that the ECH improved blood sugar levels, insulin resistance, leptin resistance, and lipid peroxidation. It can restore kisspeptin 1 (KiSS1), G protein-coupled receptor GPR 54, suppressor of cytokine signaling 3 (SOCS-3), and sirtuin 1 (SIRT1) messenger ribonucleic acid (mRNA) expression in the hypothalamus and recover sex hormone level. Thus, this study confirmed the antioxidant, anti-inflammatory, and steroidogenesis effects of CTE.

Identification and characterisation of the epididymal proteins in the lizard, Eutropis carinata (Reptilia, Squamata) (Schneider, 1801)

Lizards are seasonal breeders. Cyclic reproductive nature makes lizard as a useful model for the study of the reproductively active protein secretions in the epididymis. During breeding season, the epididymides of the lizard secret proteins that mixes with the spermatozoa and create a favourable environment for sperm maturation. In this spectrum, the aim of this study is to identify and characterize proteins which are present in the lumen of the epididymis of the lizard, E. carinata during the active phase of reproduction. The identification and analysis of the proteins are done through the proteomic approaches. The epididymal luminal fluid sample was taken from the reproductively active and inactive phase and these are subjected to the size exclusion chromatography. Two major peaks (peak 1 and peak 2) were obtained in the epididymal luminal fluid sample taken during the reproductively active phase. On the other hand, the sample from the reproductively inactive phase showed one peak (peak 1) whereas, peak 2 is not present during this phase. The peak 2 belong to reproductively active phase was later subjected to the proteomic analysis. Appropriate gel electrophoresis separation and purification methods are combined with LC-MS/MS in order to identify and characterize the proteins that are presented during the reproductively active phase. Further, in this work, nine proteins are identified including three enzymes and three heat shock proteins. Among the identified proteins, bioinformatics analysis predicts that majority of them are localized in the cytoplasm. In addition to this, an observation is made in the endoplasmic reticulum where it is seen that a close protein-protein interaction network of three molecular chaperones are involved in protein processing. Overall, this paper opens up a new dimension search for epididymal markers for the first time in reptiles, particularly lizards.

Lactoferrin increases sperm membrane functionality of frozen equine semen

During cryopreservation, sperm was submitted to an increase in reactive oxygen species generation. This work aimed to improve the quality of frozen equine sperm after the addition of antioxidants lactoferrin (Lf) and catalase (Cat) to a freezing extender. Semen from six stallions was frozen with the extenders: F1) control, INRA 82 freezing extender, F2) F1 + 500 μg/ml Lf and F3) F1 + 200 IU/ml Cat. After thawing, sperm motility parameters, membrane functionality and integrity, and acrosome integrity and spontaneous acrosome-reacted sperm were evaluated with a computer-assisted sperm analysis, a hypoosmotic swelling test and epifluorescent microscopy, respectively. Nitrite, hydroperoxide and iron concentrations of frozen semen were measured with spectrophotometry. The percentage of functional membrane sperm treated with Lf was higher (50.7% ± 11.6%) compared to that of the control (37.6% ± 15.6%), while the iron (61.4 ± 11.6 vs 73.3 ± 13.8 mg/dl) and nitrite concentrations (16.3 ± 7.1 vs 25.9 ± 4.2 μM/μg protein) were lower, respectively (p < .05). Thus, it can be suggested that Lf protect stallion spermatozoon during freezing as it has increased the percentage of sperm with functional membrane and decreased the lipid oxidant agents.

Seasonal changes in the protein profile and enzyme activity of the epididymal luminal fluid in the lizard, Eutropis carinata (Schneider, 1801)

The epididymis of the male reproductive system is known to be involved in sperm maturation via the production of polypeptides, glycoproteins, surface proteins, enzymes and other factors. During the annual reproductive cycle, the epididymis of the lizard Eutropis carinata undergoes dramatic changes, both morphologically and biochemically, that occur in a well-organized sequence. The present study reveals the sequential changes that occur in the production and concentration of proteins in the epididymal luminal fluid throughout the annual reproductive cycle. A one-dimensional electrophoretic profile of the epididymal luminal proteins revealed a total of 18 bands in the regenerative phase, 22 bands during breeding and 17 bands in the post-breeding as well as regressed phases of the reproductive cycle. By two-dimensional electrophoresis, the protein complexes that are unique to the breeding phase were further resolved based on their pI and the molecular weight of each protein of the protein complex was determined. This is the first study to observe that proteins that are present during the reproductively inactive phase disappear during the reproductively active phase. The Periodic Acid Schiff (PAS) test for protein profiles revealed the presence of proteins with a carbohydrate moiety. Certain enzymes, such as acid phosphatase, alkaline phosphatase, and α-glucosidase, are highly sensitive to seasonal changes and their activity parallels the production of the epididymal proteins. This study provides evidence for androgen-dependent cyclical changes in the pattern of protein profiles and enzyme activity of the epididymal lumen in the lizard E. carinata.

Relationship between HSP90a, NPC2 and L-PGDS proteins to boar semen freezability

BACKGROUND

The purpose of this study was to determine the association of three proteins involved in sperm function on the freezability of porcine semen: the heat shock protein 90 alpha (HSP90a), the Niemann-Pick disease type C2 protein (NPC2), and lipocalin-type prostaglandin D synthase (L-PGDS). Six adult boars (each boar was ejaculated three times, 18 in total) were classified by freezability based on the percentage of functionally competent sperm. The male semen with highest freezability (MHF) and the male semen with lowest freezability (MLF) were centrifuged immediately after collection to separate seminal plasma and spermatozoa to make four possible combinations of these two components and to incubate them for 3 h, adjusting the temperature to 17 °C, to freeze them afterwards. The quantification of proteins was performed in two stages: at zero and at 3 h after incubation of the four combinations.

RESULTS

The spermatozoa × incubation time (IT) interaction only had effect (P < 0.01) on HSP90a levels; this protein increased in seminal plasma, after 3 h of incubation, in larger quantity (P < 0.05) in combinations with MLF spermatozoa. In relation with the NPC2 protein, two isoforms of 16 and 19 kDa were identified. The 19 kDa isoform was affected (P < 0.01) only by the seminal plasma × IT interaction, with superior values (P < 0.01) both at zero and three hours of incubation, in the combinations with MHF seminal plasma; and 16 kDa isoform was affected (P < 0.01) only by the IT with reduction after 3 h of incubation. The levels of L-PGDS was affected (P < 0.01) only by the spermatozoa × IT interaction, which reduced (P < 0.01) in combinations with MLF spermatozoa after 3 h of incubation.

CONCLUSIONS

It is possible to consider that the three proteins evaluated were associated with freezability of boar semen due, especially, to the fact that mixtures with MLF spermatozoa showed greater increase levels of the HSP90a protein and reduction of L-PGDS in plasma. In addition, the seminal plasma of MHF had higher concentration of the NPC2 of 19 kDa protein, which was reduced by incubating with MHF spermatozoa.

Fatty acid content in epididymal fluid and spermatozoa during sperm maturation in dogs

Background

During sperm maturation, there is a reorganization of fatty acids from plasmatic membrane of the spermatozoa, which allows higher membrane integrity and acquisition of sperm motility. However, the fatty acid profile during sperm maturation remains unclear in dogs. Thus, the aim of this study was to identify the fatty acids from the epididymal spermatozoa and plasma during the sperm maturation, and observed changes in the motility and plasmatic membrane parameters. Twenty one adult dogs were used, subsequently to bilateral orchiectomy and epididymal storage, sperm samples were collected from the different segments of the epididymis. Samples were evaluated for conventional microscopy, computer-assisted motility analysis, sperm plasma membrane permeability and the fatty acid analysis (lipids were extracted, transmethylated and analyzed by chromatography).

Results

Caput and corpus sperm showed lower values for the motility variables evaluated and plasmatic membrane integrity, indicating different levels of the fatty acids organization. Saturated, monounsaturated and polyunsaturated fatty acids were in higher concentrations in the spermatozoa from epididymis cauda. Highlighting the presence of caprylic, stearic and docosahexaenoic acids.

Conclusions

These findings demonstrate the influence of the fatty acid profile during sperm maturation, assigning physical and chemical changes in sperm cells, essential for fertilization.

Proteome profiling of the sperm maturation milieu in the rhesus monkey (Macaca mulatta) epididymis

The mammalian spermatozoon acquires its fertilising potential during transit through the epididymis, where it interacts with epididymal luminal fluid proteins (the sperm maturation milieu). In order to highlight the epididymal-specific function of the rhesus monkey (Macaca mulatta) in sperm maturation, two-dimensional gel electrophoresis of epididymal luminal fluid proteins was followed by identification by Matrix-Assisted Laser Desorption/ Ionization Time of Flight Mass Spectrometry (MALDI-TOF/MS) or MALDI-TOF/TOF and revealed over five hundred spots, comprising 198 non-redundant proteins. Some mass spectrometric data were confirmed by western blotting identification. Some common epididymal fluid proteins were identified, such as clusterin, α-1-antitrypsin, malate dehydrogenase, L-lactate dehydrogenase B, α-1-acid glycoprotein 1 and α-mannosidase. More than 7% of all proteins were anti-oxidative, which might control oxidative stress within the male tract. When compared with bull and human epididymal luminal fluid proteins, those in the rhesus monkey had more overlap with the human, which provides evidence of a close evolutionary relationship between the rhesus monkey and man. This study provides new proteomic information on possible rhesus monkey epididymal functions and novel potential biomarkers for the noninvasive assessment of male fertility.

In-depth Proteomic mapping of mouse (Mus musculus) epididymal constructive basis for sperm maturation

BACKGROUND

The mouse epididymis performs an essential role in sperm maturation, but global protein expression data in mouse epididymis are still lacking. Here, we reported the first in-depth gel-based profiling of mouse epididymis proteome and established a 2-DE map.

RESULTS

A total of 832 protein spots were detected in the reproducible gels, and 625 spots corresponding to 355 unique protein entries have been successfully identified by MALDI-TOF-MS. The confidence of proteome data was validated by Western blot. Functional annotations showed that these proteins were mainly related to general metabolism, antioxidant and structural molecule activity. Immunohistochemistry disclosed two structural proteins (myosin regulatory light polypeptide 9 and alpha-2 type I collagen) continuously expressed in the myoid cell since postpartum.

CONCLUSION

This study provides a first-draft reference map of the mouse epididymis proteome, which will greatly expand the knowledge of the epididymal structural basis and contribute to the better understanding of those proteins in the process of mouse epididymal sperm maturation.

Two-dimensional polyacrylamide gel electrophoresis of Bali bull (Bos javanicus) seminal plasma proteins and their relationship with semen quality

The present study evaluated the relationship between Bali bull (Bos javanicus) seminal plasma proteins and different semen quality parameters. Semen samples from 10 mature Bali bulls were evaluated for conventional semen parameters (general motility, viability, and normal morphology), sperm functionality (acrosome reaction, sperm penetration rate, sperm penetration index), sperm kinetics (computer-assisted semen analysis parameters such as sperm velocity), and sperm morphology (acrosome and membrane integrity). Frozen-thawed semen with higher sperm motility, viability, acrosome integrity, and membrane integrity (P < 0.05) are consistently higher in acrosome reaction and sperm penetration assay. Three bulls showed the highest, four bulls displayed the medium, and the remaining three bulls showed the lowest for all sperm parameters and SPA. The proteome maps of seminal plasma from high-quality and low-quality Bali bulls were also established. Seminal plasma of both high-quality and low-quality Bali bulls was subjected to two-dimensional SDS-PAGE with isoelectric point ranged from 3 to 10 and molecular weight from 10 to 250 kDa. Approximately 116 spots were detected with Blue Silver stain, and of these spots, 29 were selected and identified by MALDI-TOF/TOF-MS/MS. A majority of the proteins visualized in the seminal plasma two-dimensional maps was successfully identified. An essential group of the identified spots represented binder of sperm 1 (BSP1), clusterin, spermadhesin, tissue inhibitor of metalloproteinases 2 (TIMP-2), and phospholipase A2 (PLA2). Other proteins found in high abundance included seminal ribonuclease, serum albumin, cationic trypsin, and peptide similar to β2 microglobulin. Thus, a reference map of Bali bull seminal plasma proteins has been generated for the very first time and can be used to relate protein pattern changes to physiopathologic events that may influence Bali bull reproductive performance.

Investigation of the stallion sperm proteome by mass spectrometry

Stallion spermatozoa continue to present scientific and clinical challenges with regard to the biological mechanisms responsible for their survival and function. In particular, deeper understanding of sperm energy metabolism, defence against oxidative damage and cell–cell interactions should improve fertility assessment and the application of advanced reproductive technologies in the equine species. In this study, we used highly sensitive LC–MS/MS technology and sequence database analysis to identify and characterise the proteome of Percoll-isolated ejaculated equine spermatozoa, with the aim of furthering our understanding of this cell's complex biological machinery. We were able to identify 9883 peptides comprising 1030 proteins, which were subsequently attributed to 975 gene products. Gene ontology analysis for molecular and cellular processes revealed new information about the metabolism, antioxidant defences and receptors of stallion spermatozoa. Mitochondrial proteins and those involved in catabolic processes constituted dominant categories. Several enzymes specific to β-oxidation of fatty acids were identified, and further experiments were carried out to ascertain their functional significance. Inhibition of carnitine palmitoyl transferase 1, a rate-limiting enzyme of β-oxidation, reduced motility parameters, indicating that β-oxidation contributes to maintenance of motility in stallion spermatozoa.

Spermatozoa from mice deficient in Niemann-Pick disease type C2 (NPC2) protein have defective cholesterol content and reduced in vitro fertilising ability

The cholesterol content of the sperm membrane is regulated during both maturation in the epididymis and capacitation in the female tract, two processes required for the spermatozoa to acquire their fertilising ability. Because Niemann-Pick disease, type C2 (NPC2) protein is one of the most abundant components of the epididymal fluid and contains a functional cholesterol-binding site that can transfer cholesterol between membranes, it has been suggested for years that NPC2 could be involved in the regulation of cholesterol levels in spermatozoa during epididymal maturation. In the present study, western blot and immunohistochemistry analyses demonstrated significant levels of NPC2 in the mouse epididymal epithelium. Epididymal spermatozoa obtained from NPC2(-/-) mice were morphologically normal and had normal motility parameters, but had a reduced cholesterol content compared with that of wild-type (WT) spermatozoa, as determined by both biochemical and by flow cytometry analyses. These results suggest that NPC2 could be involved in regulating cholesterol levels in spermatozoa during epididymal maturation. To understand the relevance of epididymal NPC2 for sperm function, the ability of spermatozoa to undergo events influenced by epididymal maturation, such as capacitation and fertilisation, were compared between WT and NPC2(-/-) mice. Capacitated NPC2(-/-) spermatozoa exhibited defective tyrosine phosphorylation patterns and a reduced ability to fertilise cumulus-oocyte complexes compared with WT spermatozoa, supporting the relevance of mouse epididymal NPC2 for male fertility.

Bactericidal/permeability-increasing protein originates in both the testis and the epididymis and localizes in mouse spermatozoa

Bactericidal/permeability-increasing protein (BPI) is an endogenous antibiotic protein with activity against gram-negative bacteria. In the present study, we examined the expression of BPI in postnatal mouse testes and epididymides as well as the subcellular localization within epididymal spermatozoa. Our results showed that, BPI mRNA was expressed in testis and epididymis independently. Throughout the epididymis, the BPI protein level gradually decreased in the epididymal epithelium in a spatial manner, specialized within the cytoplasm of clear cells in the cauda part. We detected BPI proteins in intact acrosome, implying its testicular origin; on the other hand, after the acrosome reaction, BPI proteins were observed dispersed across the entire sperm head, especially enriched at the equatorial segment. Our findings suggested a dual origin of the BPI that generated both in the testis and epididymis, and associated with mouse spermatozoa. BPI protein might be involved in the dynamics modification of the sperm plasma membrane and also the fertilization process.

Niemann–Pick disease type C2 protein induces triglyceride accumulation in silkworm and mammalian cell lines

Niemann–Pick disease type C2 protein was identified as a triglyceride-accumulating factor in insect fluid.

New insights into epididymal function in relation to sperm maturation

Testicular spermatozoa acquire fertility only after 1 or 2 weeks of transit through the epididymis. At the end of this several meters long epididymal tubule, the male gamete is able to move, capacitate, migrate through the female tract, bind to the egg membrane and fuse to the oocyte to result in a viable embryo. All these sperm properties are acquired after sequential modifications occurring either at the level of the spermatozoon or in the epididymal surroundings. Over the last few decades, significant increases in the understanding of the composition of the male gamete and its surroundings have resulted from the use of new techniques such as genome sequencing, proteomics combined with high-sensitivity mass spectrometry, and gene-knockout approaches. This review reports and discusses the most relevant new results obtained in different species regarding the various cellular processes occurring at the sperm level, in particular, those related to the development of motility and egg binding during epididymal transit.