The contribution of proteomics to understanding epididymal maturation of mammalian spermatozoa

Phosphoproteomic analysis of the adaption of epididymal epithelial cells to corticosterone challenge

BACKGROUND

The epididymis has long been of interest owing to its role in promoting the functional maturation of the male germline. More recent evidence has also implicated the epididymis as an important sensory tissue responsible for remodeling of the sperm epigenome, both under physiological conditions and in response to diverse forms of environmental stress. Despite this knowledge, the intricacies of the molecular pathways involved in regulating the adaptation of epididymal tissue to paternal stressors remains to be fully resolved.

OBJECTIVE

The overall objective of this study was to investigate the direct impact of corticosterone challenge on a tractable epididymal epithelial cell line (i.e., mECap18 cells), in terms of driving adaptation of the cellular proteome and phosphoproteome signaling networks.

MATERIALS AND METHODS

The newly developed phosphoproteomic platform EasyPhos coupled with sequencing via an Orbitrap Exploris 480 mass spectrometer, was applied to survey global changes in the mECap18 cell (phospho)proteome resulting from sub-chronic (10-day) corticosterone challenge.

RESULTS

The imposed corticosterone exposure regimen elicited relatively subtle modifications of the global mECap18 proteome (i.e., only 73 out of 4171 [∼1.8%] proteins displayed altered abundance). By contrast, ∼15% of the mECap18 phosphoproteome was substantially altered following corticosterone challenge. In silico analysis of the corresponding parent proteins revealed an activation of pathways linked to DNA damage repair and oxidative stress responses as well as a reciprocal inhibition of pathways associated with organismal death. Corticosterone challenge also induced the phosphorylation of several proteins linked to the biogenesis of microRNAs. Accordingly, orthogonal validation strategies confirmed an increase in DNA damage, which was ameliorated upon selective kinase inhibition, and an altered abundance profile of a subset of microRNAs in corticosterone-treated cells.

CONCLUSIONS

Together, these data confirm that epididymal epithelial cells are reactive to corticosterone challenge, and that their response is tightly coupled to the opposing action of cellular kinases and phosphatases.

Single-cell and spatial transcriptomic investigation reveals the spatiotemporal specificity of the beta-defensin gene family during mouse sperm maturation

Low sperm motility is a significant contributor to male infertility. beta-defensins have been implicated in host defence and the acquisition of sperm motility; however, the regulatory mechanisms governing their gene expression patterns and functions remain poorly understood. In this study, we performed single-cell RNA and spatial transcriptome sequencing to investigate the cellular composition of testicular and epididymal tissues and examined their gene expression characteristics. In the epididymis, we found that epididymal epithelial cells display a region specificity of gene expression in different epididymal segments, including the beta-defensin family genes. In particular, Defb15, Defb18, Defb20, Defb25 and Defb48 are specific to the caput; Defb22, Defb23 and Defb26 to the corpus; Defb2 and Defb9 to the cauda of the epididymis. To confirm this, we performed mRNA fluorescence in situ hybridisation (FISH) targeting certain exon region of beta-defensin genes, and found some of their expression matched the sequencing results and displayed a close connection with epididimosome marker gene Cd63. In addition, we paid attention to the Sertoli cells and Leydig cells in the testis, along with fibroblasts and smooth muscle cells in the epididymis, by demonstrating their gene expression profile and spatial information. Our study provides a single-cell and spatial landscape for analysing the gene expression characteristics of testicular and epididymal environments and has important implications for the study of spermatogenesis and sperm maturation.

Bringing proteomics to bear on male fertility: key lessons

INTRODUCTION

Male infertility is a major public health concern globally. Proteomics has revolutionized our comprehension of male fertility by identifying potential infertility biomarkers and reproductive defects. Studies comparing sperm proteome with other male reproductive tissues have the potential to refine fertility diagnostics and guide infertility treatment development.

AREAS COVERED

This review encapsulates literature using proteomic approaches to progress male reproductive biology. Our search methodology included systematic searches of databases such as PubMed, Scopus, and Web of Science for articles up to 2023. Keywords used included 'male fertility proteomics,' 'spermatozoa proteome,' 'testis proteomics,' 'epididymal proteomics,' and 'non-hormonal male contraception.' Inclusion criteria were robust experimental design, significant contributions to male fertility, and novel use of proteomic technologies.

EXPERT OPINION

Expert analysis shows a shift from traditional research to an integrative approach that clarifies male reproductive health's molecular intricacies. A gap exists between proteomic discoveries and clinical application. The expert opinions consolidated here not only navigate the current findings but also chart the future proteomic applications for scientific and clinical breakthroughs. We underscore the need for continued investment in proteomic research - both in the technological and collaborative arenas - to further unravel the secrets of male fertility, which will be central to resolving fertility issues in the coming era.

Morphology of the epididymal duct of the domestic pig (Sus scrofa domesticus)

The study provides a general overview of the morphology of the epididymal duct in pigs. Four epididymides from two sexually mature boars were dissected into 32 segments and examined histologically. Duct lumen and wall thickness were measured and relative surface area of different components was assessed by Chalkley's random hit method. The epithelial lining was characterized at X1000. Lumen diameter and wall thickness of efferent ductules averaged 177 and 30 µm, respectively. Of the epididymal duct from caput to distal corpus the luminal diameter was 332 µm, with a narrower section in the proximal corpus. Wall thickness averaged 70 µm. In the cauda, luminal diameter and wall thickness increased to 717 and 751 µm, respectively. The epithelial lining of the efferent ductules consists of a single layer of columnar cells with average height 21 µm. The lining of the epididymal duct consists of ciliated, pseudo-stratified columnar epithelium composed of "basal cells" and "principal cells." Particularly tall principal cells (96 µm) were found in the proximal caput. Height decreased to 40 µm at the distal cauda. Microvilli from principal cells were 14-17 µm long in the distal caput but decreased to 5 µm in the distal cauda. The epithelial lining was folded in the proximal caput and more so in the distal cauda. Secretory granules (epididymosomes) were present in small amounts in efferent ductules and epididymal duct; the largest quantities occurred in the distal cauda. Leukocytes were present throughout the duct, albeit in insignificant numbers. Chalkley's random hit method showed rapid spermatozoan transport through efferent ductules and proximal caput in large amounts of fluid. Sperm concentration increased due to fluid resorption in the proximal caput, was highest from caput flexure to proximal cauda and decreased at the caudal flexure, indicating secretory activity.

Non-targeted proteomic analysis of Asian elephant (Elephas maximus) seminal plasma using an in-solution digestion technique and liquid chromatography tandem-mass spectrometry

Seminal plasma proteins have recently been reported to play a significant role as valuable materials for understanding male reproductive biology, identifying causes of fertility problems, and developing reproductive biomarkers. Proteomic analysis of seminal plasma holds promise in advancing the understanding of male Asian elephant reproductive biology. This study aims to explore seminal plasma proteins of Asian elephants and their probable functions to provide fundamental information about male reproduction in this species. The protein solution from pooled seminal plasma from 10 bulls (a total of 33 ejaculates) was digested into peptides and identified using LC-MS/MS. Out of 986 proteins, 597 were mapped and matched with 58 species in UniProt databases, including Elephas maximus. These mapped proteins were mostly involved in binding function, catalytic activity, cellular process, and metabolic process. Only 29 mapped proteins were recognized to be related in reproductive process, mainly associated in spermatogenesis and sperm capacitation. Additionally, several seminal plasma proteins related to fertility or semen quality in other mammals were also found in Asian elephant semen, such as keratin type I, aldose reductase, thrombospondon-1, fibronectin 1, platelet-activating factor acetyl hydrolase, mannosidase, and semenogelin-2. This discovery clearly reveals the beneficial protein profile in seminal plasma of the Asian elephant and serves as a crucial step in investigating infertility and poor semen quality in this valuable species.

Comparative Analysis of Epididymis Cauda of Yak before and after Sexual Maturity

Epididymis development is the basis of male reproduction and is a crucial site where sperm maturation occurs. In order to further understand the epididymal development of yak and how to regulate sperm maturation, we conducted a multi-omics analysis. We detected 2274 differential genes, 222 differential proteins and 117 co-expression genes in the cauda epididymis of yak before and after sexual maturity by RNA-seq and proteomics techniques, which included TGFBI, COL1A1, COL1A2, COL3A1, COL12A1, SULT2B1, KRT19, and NPC2. These high abundance genes are mainly related to cell growth, differentiation, adhesion and sperm maturation, and are mainly enriched via extracellular matrix receptor interaction, protein differentiation and absorption, and lysosome and estrogen signaling pathways. The abnormal expression of these genes may lead to the retardation of epididymal cauda development and abnormal sperm function in yak. In conclusion, through single and combined analysis, we provided a theoretical basis for the development of the yak epididymal cauda, sperm maturation, and screening of key genes involved in the regulation of male yak reproduction.

Sortilin knock-down alters the expression and distribution of cathepsin D and prosaposin and up-regulates the cation-dependent mannose-6-phosphate receptor in rat epididymal cells

The selective transport to lysosomes can be mediated by either mannose-6-phosphate receptors (CD-MPR and CI-MPR) or sortilin. In mammalian epididymis, some lysosomal proteins are secreted into the lumen through unknown mechanisms. To investigate the underlying mechanisms of lysosomal protein transport in epididymal cells we studied the expression and distribution of cathepsin D (CatD) and prosaposin (PSAP) in a sortilin knocked down RCE-1 epididymal cell line (RCE-1 KD) in comparison with non-transfected RCE-1 cells. In RCE-1 cells, CatD was found in the perinuclear zone and co-localize with sortilin, whereas in RCE-1 KD cells, the expression, distribution and processing of the enzyme were altered. In turn, PSAP accumulated intracellularly upon sortilin knock-down and redistributed from LAMP-1-positive compartment to a perinuclear location, remaining co-localized with CatD. Interestingly, the sortilin knock-down induced CD-MPR overexpression and a redistribution of the receptor from the perinuclear zone to a dispersed cytoplasmic location, accompanied by an increased co-localization with CatD. The increase in CD-MPR could result from a compensatory response for the proper delivery of CatD to lysosomes in epididymal cells. The intracellular pathway taken by lysosomal proteins could be an approach for addressing further studies to understand the mechanism of exocytosis and therefore the role of these proteins in the epididymis.

Microfluidics facilitating the use of small extracellular vesicles in innovative approaches to male infertility

Sperm are transcriptionally and translationally quiescent and, therefore, rely on the seminal plasma microenvironment for function, survival and fertilization of the oocyte in the oviduct. The male reproductive system influences sperm function via the binding and fusion of secreted epididymal (epididymosomes) and prostatic (prostasomes) small extracellular vesicles (S-EVs) that facilitate the transfer of proteins, lipids and nucleic acids to sperm. Seminal plasma S-EVs have important roles in sperm maturation, immune and oxidative stress protection, capacitation, fertilization and endometrial implantation and receptivity. Supplementing asthenozoospermic samples with normospermic-derived S-EVs can improve sperm motility and S-EV microRNAs can be used to predict non-obstructive azoospermia. Thus, S-EV influence on sperm physiology might have both therapeutic and diagnostic potential; however, the isolation of pure populations of S-EVs from bodily fluids with current conventional methods presents a substantial hurdle. Many conventional techniques lack accuracy, effectiveness, and practicality; yet microfluidic technology has the potential to simplify and improve S-EV isolation and detection.

Momordica charantia fruit extract with antioxidant capacity improves the expression of tyrosine-phosphorylated proteins in epididymal fluid of chronic stress rats

OBJECTIVE

Although the protective effects of Momordica charantia L. (MC) extract on chemical-induced testicular damage have been studied, the preventive effects of MC extract on functional proteins in the epididymis under chronic stress have never been reported. This study investigated the protective effects of MC fruit extract on protein secretion, especially tyrosine-phosphorylated proteins, in the epididymis of rats exposed to chronic unpredictable stress (CUS).

METHODS

Total phenolic compounds (TPC), total flavonoid compounds (TFC) and antioxidant capacities of MC extract were measured. Adult male rats were divided into 4 groups: control group, CUS group, and 2 groups of CUS that received different doses of MC extract (40 or 80 mg/kg). In treated groups, rats were given MC daily, followed by induction of CUS (1 stressor was randomly applied from a battery of 9 potential stressors) for 60 consecutive days. Plasma corticosterone and testosterone levels were analyzed after the end of experiment. Expressions of heat-shock protein 70 (HSP-70) and tyrosine-phosphorylated proteins present in the fluid of the head and tail of the epididymis were quantified using Western blot.

RESULTS

MC extract contained TPC of (19.005 ± 0.270) mg gallic acid equivalents and TFC of (0.306 ± 0.012) mg catechin equivalents per gram, and had 2,2-diphenyl-1-picrylhydrazyl antioxidant capacity of (4.985 ± 0.086) mg trolox equivalents per gram, radical 50% inhibitory concentration of (2.011 ± 0.008) mg/mL and ferric reducing antioxidant power of (23.697 ± 0.819) µmol Fe(II) per gram. Testosterone level in the epididymis was significantly increased, while the corticosterone level was significantly improved in groups treated with MC extract, compared to the CUS animals. Particularly, an 80 mg/kg dose of MC extract prevented the impairments of HSP-70 and tyrosine-phosphorylated protein expressions in the luminal fluid of the epididymis of CUS rats.

CONCLUSION

MC fruit extract had antioxidant activities and improved the functional proteins secreted from the head and tail of the epididymis. It is possible to develop the MC fruit extract as a male fertility supplement for enhancing functional sperm maturation in stressed men.

How does the boar epididymis regulate the emission of fertile spermatozoa?

The epididymis is responsible for peripheral immune tolerance of maturing spermatozoa even though these have xeno-antigens foreign to the male and female immune system. The epididymis also produces factors required for fertilization and serves as a sperm repository until the time of ejaculation. These reproduction-relevant epididymal functions occur in the mesonephros-derived duct-system that is composed of absorptive and secretory epithelial cells with the capacity for merocrine and apocrine secretion of proteins, antioxidative- and electrolyte/pH-regulating enzymes and small, non-coding RNAs (sncRNAs), many stored in epididymosomes for sperm adhesion and long-lasting modifications of sperm functions. This paper provides a review summary of current and new knowledge of how the boar epididymis affects the quality of spermatozoa in the ejaculate of breeding boars. There is a particular focus on sperm maturation, survival, function and the role of signaling to the female immune system in fertility modulation. Furthermore, aspects related to the ductus epithelial contributions regarding electrolyte control, protein production, release of epididymosomes that contain sncRNAs are emphasized as are novel associations with fertility of the male, sperm quiescence during storage in the cauda epididymis, and on changes occurring in sperm subsequent to ejaculation.

Sperm acquire epididymis-derived proteins through epididymosomes

STUDY QUESTION

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

SUMMARY ANSWER

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

WHAT IS KNOWN ALREADY

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

STUDY DESIGN, SIZE, DURATION

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

PARTICIPANTS/MATERIALS, SETTING, METHODS

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

MAIN RESULTS AND THE ROLE OF CHANCE

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

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

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

WIDER IMPLICATIONS OF THE FINDINGS

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

STUDY FUNDING/COMPETING INTEREST(S)

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

Seminal Levels of Omentin-1/ITLN1 in Inflammatory Conditions Related to Male Infertility and Localization in Spermatozoa and Tissues of Male Reproductive System

Purpose

Omentin-1/intelectin (ITLN)1 is an adipocytokine with both anti-inflammatory and anti-oxidative stress properties, and little is known about its role in male reproduction. This study was aimed at exploring the relationships among omentin-1/ITLN1, semen parameters and F₂-isoprostanes (F₂-IsoPs), a maker of oxidative stress, in groups of patients affected by different pathologies. In addition, omentin-1/ITLN1 immunolocalization was assessed in ejaculated spermatozoa and in tissues of male reproductive system.

Patients and Methods

Semen samples of infertile patients with varicocele (n = 27), genitourinary infections (n = 17), idiopathic infertility (n = 15) and fertile men (n = 21) were analyzed following WHO guidelines, and seminal plasma were used to determine omentin-1/ITLN1 by ELISA and F₂-IsoP levels by gas chromatography/negative-ion chemical ionization tandem mass spectrometry. Omentin-1/ITLN1 was localized in human sperm and in the tissue of male reproductive system.

Results

Considering all participants, F₂-IsoP and omentin-1/ITLN1 levels were positively correlated (p = 0.000), and both these indices were negatively correlated with sperm parameters. Infertile patients showed lower sperm parameters than fertile ones; varicocele and infection groups had significantly increased levels of F₂-IsoPs (both p = 0.000) and omentin-1/ITLN1 (p = 0.000 and p = 0.001, respectively). Omentin-1/ITLN1 signal was located as a spot in the connecting piece (in 43.5% of cases midpiece was also labeled) of sperm from fertile men and in cytoplasmic residue and in the entire tail in sperm of patients with varicocele and genitourinary infections. A focal omentin-1/ITLN1 immunolabelling was evident in the basal area of epididymal tubule, and a diffuse signal was present in the seminal vesicle epithelium.

Conclusion

Semen omentin-1/ITLN1 originates from seminal vesicles, its levels increase in inflammatory conditions and are negatively correlated with sperm parameters. For this reason, a sort of protective role of omentin-1/ITLN1 can be postulated, as this adipokine shows anti-inflammatory properties also in many other biological systems.

Influence of the Season and Region Factor on Phosphoproteome of Stallion Epididymal Sperm

Epididymal maturation can be defined as a scope of changes occurring during epididymal transit that prepare spermatozoa to undergo capacitation. One of the most common post-translational modifications involved in the sperm maturation process and their ability to fertilise an oocyte is the phosphorylation of sperm proteins. The aim of this study was to compare tyrosine, serine, and threonine phosphorylation patterns of sperm proteins isolated from three subsequent segments of the stallion epididymis, during and out of the breeding season. Intensities of phosphorylation signals and phosphoproteins profiles varied in consecutive regions of the epididymis. However, significant differences in the phosphorylation status were demonstrated in case of endoplasmic reticulum chaperone BiP (75 and 32 kDa), protein disulfide-isomerase A3 (50 kDa), nesprin-1 (23 kDa), peroxiredoxin-5 (17 kDa), and protein bicaudal D homolog (15 kDa) for season x type of phosphorylated residues variables. Significant differences in the phosphorylation status were also demonstrated in case of endoplasmic reticulum chaperone BiP and albumin (61 kDa), protein disulfide-isomerase A3 (50 kDa), and protein bicaudal D homolog (15 kDa) for region x type of phosphorylated residues variables.

Extra-cellular vesicles of the male genital tract: new actors in male fertility?

Extracellular Vesicles (EVs) are membrane-limited particles containing proteins, lipids, metabolites and nucleic acids that are secreted by healthy and cancerous cells. These vesicles are very heterogeneous in size and content and mediate a variety of biological functions. Three subtypes of EV have been described in the male genital tract: microvesicles, myelinosomes and exosomes. Each type of EVs depends on the location of secretion such as the testis, prostate or epididymis. It has been shown that EVs can fuse together and deliver information to recipient cells, for example spermatozoa in the male genital tract. Cryo-electron microscopy remains the reference technique for determining EV morphology, but quantifying the absolute concentration of these EVs in biological fluids remains a challenge from a clinical point of view. The field of bio detection has considerably increased with the introduction of nanomaterials in biosensors and will provide a better understanding of the impact of these EVs. However, functional modifications of male gametes result from interactions with the components of the intraluminal fluid all along the genital tract and depend on the secretion and absorption of proteins and lipids from the local microenvironment. We cannot therefore exclude the possibility of epigenetic modulation of the information that will be transmitted to the embryo and therefore to the next generation via EVs.

Protein Identification of Spermatozoa and Seminal Plasma in Bottlenose Dolphin (Tursiops truncatus)

Proteins play an important role in many reproductive functions such as sperm maturation, sperm transit in the female genital tract or sperm-oocyte interaction. However, in general, little information concerning reproductive features is available in the case of aquatic animals. The present study aims to characterize the proteome of both spermatozoa and seminal plasma of bottlenose dolphins (Tursiops truncatus) as a model organism for cetaceans. Ejaculate samples were obtained from two trained dolphins housed in an aquarium. Spermatozoa and seminal plasma were analyzed by means of proteomic analyses using an LC-MS/MS, and a list with the gene symbols corresponding to each protein was submitted to the DAVID database. Of the 419 proteins identified in spermatozoa and 303 in seminal plasma, 111 proteins were shared by both. Furthermore, 70 proteins were identified as involved in reproductive processes, 39 in spermatozoa, and 31 in seminal plasma. The five most abundant proteins were also identified in these samples: AKAP3, ODF2, TUBB, GSTM3, ROPN1 for spermatozoa and CST11, LTF, ALB, HSP90B1, PIGR for seminal plasma. In conclusion, this study provides the first characterization of the proteome in cetacean sperm and seminal plasma, opening the way to future research into new biomarkers, the analysis of conservation capacity or possible additional applications in the field of assisted reproductive technologies.

CEP164 is essential for efferent duct multiciliogenesis and male fertility

Cilia are evolutionarily conserved microtubule-based structures that perform diverse biological functions. Cilia are assembled on basal bodies and anchored to the plasma membrane via distal appendages. In the male reproductive tract, multicilia in efferent ducts (EDs) move in a whip-like motion to prevent sperm agglutination. Previously, we demonstrated that the distal appendage protein CEP164 recruits Chibby1 (Cby1) to basal bodies to facilitate basal body docking and ciliogenesis. Mice lacking CEP164 in multiciliated cells (MCCs) (FoxJ1-Cre;CEP164fl/fl) show a significant loss of multicilia in the trachea, oviduct, and ependyma. In addition, we observed male sterility; however, the precise role of CEP164 in male fertility remained unknown. Here, we report that the seminiferous tubules and rete testis of FoxJ1-Cre;CEP164fl/fl mice exhibit substantial dilation, indicative of dysfunctional multicilia in the EDs. We found that multicilia were hardly detectable in the EDs of FoxJ1-Cre;CEP164fl/fl mice although FoxJ1-positive immature cells were present. Sperm aggregation and agglutination were commonly noticeable in the lumen of the seminiferous tubules and EDs of FoxJ1-Cre;CEP164fl/fl mice. In FoxJ1-Cre;CEP164fl/fl mice, the apical localization of Cby1 and the transition zone marker NPHP1 was severely diminished, suggesting basal body docking defects. TEM analysis of EDs further confirmed basal body accumulation in the cytoplasm of MCCs. Collectively, we conclude that male infertility in FoxJ1-Cre;CEP164fl/fl mice is caused by sperm agglutination and obstruction of EDs due to loss of multicilia. Our study, therefore, unravels an essential role of the distal appendage protein CEP164 in male fertility.

Role of Exosomes in the Exchange of Spermatozoa after Leaving the Seminiferous Tubule: A Review

BACKGROUND

Exosomes are extracellular vesicles (EVs) released from cells upon fusion of an intermediate endocytic compartment with the plasma membrane. They refer to the intraluminal vesicles released from the fusion of multivesicular bodies with the plasma membrane. The contents and number of exosomes are related to diseases such as metabolic diseases, cancer and inflammatory diseases. Exosomes have been used in neurological research as a drug delivery tool and also as biomarkers for diseases. Recently, exosomes were observed in the seminal plasma of the one who is asthenozoospermia, which can affect sperm motility and capacitation.

OBJECTIVE

The main objective of this review is to deeply discuss the role of exosomes in spermatozoa after leaving the seminiferous tubule.

METHODS

We conducted an extensive search of the literature available on relationships between exosomes and exosomes in spermatozoa on the bibliographic database.

CONCLUSION

This review thoroughly discussed the role that exosomes play in the exchange of spermatozoa after leaving the seminiferous tubule and its potential as a drug delivery tool and biomarkers for diseases as well.

Aquaporins Are Differentially Regulated in Canine Cryptorchid Efferent Ductules and Epididymis

Simple Summary

The distribution and expression of aquaporins (AQPs) in the testes and spermatozoa of several animal species play important roles in spermatogenesis and spermatozoon transit in this region. The aim of this study was to evaluate AQP7, AQP8, and AQP9 localization and expression in the efferent ductules and epididymal regions (the caput, corpus, and cauda) of normal and cryptorchid dogs. The results from immunohistochemistry, Western blotting, and real-time reverse transcription polymerase chain reaction (RT-PCR) show regional tissue distributions, particularly at the level of the epithelium of efferent ductules and both the regions caput and cauda of the canine cryptorchid epididymis. These findings support the hypothesis that these channel proteins respond differently to multiple stimuli that cause cryptorchidism (hormones, heat, osmolarity, etc.) and participate in the mechanisms of cell “resilience” or apoptosis taking place in the epididymis.

Abstract

The efferent ductules and the epididymis are parts of the male reproductive system where spermatozoa mature. Specialized epithelial cells in these ducts contribute to the transport of fluids produced by spermatozoa’s metabolic activity. Aquaporins (AQPs) have been demonstrated to be expressed in the spermatozoan membrane and testis epithelial cells, where they contribute to regulating spermatozoan volume and transit through environments of differing osmolality. Due to the lack of detailed literature regarding AQP expression in the canine male genital tract, the aim of this study was to investigate both the distribution and expression of AQP7, AQP8, and AQP9 in the efferent ductules and epididymal regions (caput, corpus, and cauda) from normal and cryptorchid dogs by using immunohistochemistry, Western blotting, and real-time reverse transcription polymerase chain reaction (RT-PCR). Our results show different patterns for the distribution and expression of the examined AQPs, with particular evidence of their upregulation in the caput and downregulation in the cauda region of the canine cryptorchid epididymis. These findings are associated with a modulation of Hsp70 and caspase-3 expression, suggesting the participation of AQPs in the luminal microenvironment modifications that are peculiar characteristics of this pathophysiological condition.

Dynamics of cattle sperm sncRNAs during maturation, from testis to ejaculated sperm

Background

During epididymal transit, spermatozoa go through several functional maturation steps, resulting from interactions with epididymal secretomes specific to each region. In particular, the sperm membrane is under constant remodeling, with sequential attachment and shedding of various molecules provided by the epididymal lumen fluid and epididymosomes, which also deliver sncRNA cargo to sperm. As a result, the payload of sperm sncRNAs changes during the transit from the epididymis caput to the cauda. This work was designed to study the dynamics of cattle sperm sncRNAs from spermatogenesis to final maturation.

Results

Comprehensive catalogues of sperm sncRNAs were obtained from testicular parenchyma, epididymal caput, corpus and cauda, as well as ejaculated semen from three Holstein bulls. The primary cattle sncRNA sperm content is markedly remodeled as sperm mature along the epididymis. Expression of piRNAs, which are abundant in testis parenchyma, decreases dramatically at epididymis. Conversely, sperm progressively acquires miRNAs, rsRNAs, and tsRNAs along epididymis, with regional specificities. For instance, miRNAs and tsRNAs are enriched in epididymis cauda and ejaculated sperm, while rsRNA expression peaks at epididymis corpus. In addition, epididymis corpus contains mainly 20 nt long piRNAs, instead of 30 nt in all other locations. Beyond the bulk differences in abundance of sncRNAs classes, K-means clustering was performed to study their spatiotemporal expression profile, highlighting differences in specific sncRNAs and providing insights into their putative biological role at each maturation stage. For instance, Gene Ontology analyses using miRNA targets highlighted enriched processes such as cell cycle regulation, response to stress and ubiquitination processes in testicular parenchyma, protein metabolism in epididymal sperm, and embryonic morphogenesis in ejaculated sperm.

Conclusions

Our findings confirm that the sperm sncRNAome does not simply reflect a legacy of spermatogenesis. Instead, sperm sncRNA expression shows a remarkable level of plasticity resulting probably from the combination of multiple factors such as loss of the cytoplasmic droplet, interaction with epididymosomes, and more surprisingly, the putative in situ production and/or modification of sncRNAs by sperm. Given the suggested role of sncRNA in epigenetic trans-generational inheritance, our detailed spatiotemporal analysis may pave the way for a study of sperm sncRNAs role in embryo development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13072-021-00397-5.

Chronic stress affects tyrosine phosphorylated protein expression and secretion of male rat epididymis

Chronic stress (CS) is shown to decrease the semen quality with changed expression of tyrosine phosphorylated (TyrPho) proteins in testicular and seminal tissues. However, the alterations of such proteins and fluid contents in the epididymis, producing sperm maturation factors, have never been reported. Sixteen adult rats were randomly divided into 2 groups (n = 8). The control animals were not subjected to stressors whereas CS rats were immobilised within restraint cage (4 hr/day) before cold forced-water swimming (15 min/day) for 60 days. Corticosterone, testosterone, blood glucose level (BGL), malondialdehyde (MDA) and biochemical components in epididymal fluid were assayed. Expressions of heat shock protein 70 (HSP-70), androgen receptor (AR) and TyrPho protein were investigated in epididymal tissue and fluid. Significantly, CS increased the corticosterone and BGL but decreased testosterone and epididymal substance levels. MDA level in tail epididymal fluid and HSP-70 expression in both regions of epididymal tissues and fluids, except in head epididymal fluid of CS were increased. Epididymal tissues showed the decrease of AR expression. Presence and changes of many TyrPho proteins were observed in CS. In conclusion, CS could affect functional proteins particularly TyrPho in epididymis, resulted in low semen quality.

Molecular insights into the divergence and diversity of post-testicular maturation strategies

Competition to achieve paternity has coerced the development of a multitude of male reproductive strategies. In one of the most well-studied examples, the spermatozoa of all mammalian species must undergo a series of physiological changes as they transit the male (epididymal maturation) and female (capacitation) reproductive tracts prior to realizing their potential to fertilize an ovum. However, the origin and adaptive advantage afforded by these intricate processes of post-testicular sperm maturation remain to be fully elucidated. Here, we review literature pertaining to the nature and the physiological role of epididymal maturation and subsequent capacitation in comparative vertebrate taxa including representative species from the avian, reptilian, and mammalian lineages. Such insights are discussed in terms of the framework they provide for helping to understand the evolutionary significance of post-testicular sperm maturation.

Role of GPER-Mediated Signaling in Testicular Functions and Tumorigenesis

Estrogen signaling plays important roles in testicular functions and tumorigenesis. Fifteen years ago, it was discovered that a member of the G protein-coupled receptor family, GPR30, which binds also with high affinity to estradiol and is responsible, in part, for the rapid non-genomic actions of estrogens. GPR30, renamed as GPER, was detected in several tissues including germ cells (spermatogonia, spermatocytes, spermatids) and somatic cells (Sertoli and Leydig cells). In our previous review published in 2014, we summarized studies that evidenced a role of GPER signaling in mediating estrogen action during spermatogenesis and testis development. In addition, we evidenced that GPER seems to be involved in modulating estrogen-dependent testicular cancer cell growth; however, the effects on cell survival and proliferation depend on specific cell type. In this review, we update the knowledge obtained in the last years on GPER roles in regulating physiological functions of testicular cells and its involvement in neoplastic transformation of both germ and somatic cells. In particular, we will focus our attention on crosstalk among GPER signaling, classical estrogen receptors and other nuclear receptors involved in testis physiology regulation.

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.

Immunohistochemical Studies of αSMA in the Epididymis of African Four-Toed Hedgehog (Atelerix albiventris)

The epididymis plays an important role in sperm maturation, storage, transport and in the secretion of enzymes and proteins into the tubular lumen. In this study, we examined the histology, microstereology and immunohistochemical localization of alpha smooth muscle (αSMA) in the three regions of the epididymis of the African four-toed hedgehog (Atelerix albiventris). Ten adult males were captured from the wild in Ibadan, Nigeria, between May and October, 2016. The animals were euthanized and the epididymis (caput, corpus and cauda regions) were retrieved and fixed in buffered neutral formalin ahead of the paraffin technique, following standard procedures. The duct of the epididymis was lined by pseudostratified columnar epithelium comprising basal, principal and apical cells as well as intraepithelial lymphocytes in proximity to basal cells. The principal cells, the major cells encountered within the epididymal epithelium of the animal, decreased in population from the caput to the cauda epididymidis while the apical cells were more abundant in the cauda epididymidis. Positive reactions to αSMA were observed in the peritubular muscular coat of the epididymal duct as well as blood vessels across the three regions of the epididymis with the caput and cauda epididymidis showing stronger positive reactions compared to the corpus epididymidis. This study demonstrated that the histology, microstereology as well as the cellular constituents of the epididymal duct of the Atelerix albiventris are similar to those of other mammals with a slight variation. It has also highlighted variation in the localization of αSMA across the regions of the epididymis of the animal.

Reciprocal surface expression of arylsulfatase A and ubiquitin in normal and defective mammalian spermatozoa

Defective mammalian spermatozoa are marked on their surface by proteolytic chaperone ubiquitin. To identify potential ubiquitinated substrates in the defective spermatozoa, we resolved bull sperm protein extracts on a two-dimensional gel and isolated a 64-65-kDa spot (p64) corresponding to one of the major ubiquitin-immunoreactive bands observed in the one-dimensional Western blots. Immune serum raised against this protein recognized a prominent, possibly glycosylated band/spot in the range of 55-68 kDa, consistent with the original spot used for immunization. Internal sequences obtained by Edman degradation of this spot matched the sequence of arylsulfatase A (ARSA), the sperm acrosomal enzyme thought to be important for fertility. By immunofluorescence, a prominent signal was detected on the acrosomal surface (boar and bull) and on the sperm tail principal piece (bull). A second immune serum raised against a synthetic peptide corresponding to an immunogenic internal sequence (GTGKSPRRTL) of the porcine ARSA also labeled sperm acrosome and principal piece. Both sera showed diminished immunoreactivity in the defective bull spermatozoa co-labeled with an anti-ubiquitin antibody. Western blotting and image-based flow cytometry (IBFC) confirmed a reduced ARSA immunoreactivity in the immotile sperm fraction rich in ubiquitinated spermatozoa. Larger than expected ARSA-immunoreactive bands were found in sperm protein extracts immunoprecipitated with anti-ubiquitin antibodies and affinity purified with matrix-bound, recombinant ubiquitin-binding UBA domain. These bands did not show the typical pattern of ARSA glycosylation but overlapped with bands preferentially binding the Lens culinaris agglutinin (LCA) lectin. By both epifluorescence microscopy and IBFC, the LCA binding was increased in the ubiquitinated spermatozoa with diminished ARSA immunoreactivity. ARSA was also found in the epididymal fluid suggesting that in addition to intrinsic ARSA expression in the testis, epididymal spermatozoa take up ARSA on their surface during the epididymal passage. We conclude that sperm surface ARSA is one of the ubiquitinated sperm surface glycoproteins in defective bull spermatozoa. Defective sperm surface thus differs from normal sperm surface by increased ubiquitination, reduced ARSA binding, and altered glycosylation.

GSTO2 Isoforms Participate in the Oxidative Regulation of the Plasmalemma in Eutherian Spermatozoa during Capacitation

In addition to perinuclear theca anchored glutathione-s-transferase omega 2 (GSTO2), whose function is to participate in sperm nuclear decondensation during fertilization (Biol Reprod. 2019, 101:368–376), we herein provide evidence that GSTO2 is acquired on the sperm plasmalemma during epididymal maturation. This novel membrane localization was reinforced by the isolation and identification of biotin-conjugated surface proteins from ejaculated and capacitated boar and mouse spermatozoa, prompting us to hypothesize that GSTO2 has an oxidative/reductive role in regulating sperm function during capacitation. Utilizing an inhibitor specific to the active site of GSTO2 in spermatozoa, inhibition of this enzyme led to a decrease in tyrosine phosphorylation late in the capacitation process, followed by an expected decrease in acrosome exocytosis and motility. These changes were accompanied by an increase in reactive oxygen species (ROS) levels and membrane lipid peroxidation and culminated in a significant decrease in the percentage of oocytes successfully penetrated by sperm during in vitro fertilization. We conclude that GSTO2 participates in the regulation of sperm function during capacitation, most likely through protection against oxidative stress on the sperm surface.

Proteomic identification of boar seminal plasma proteins related to sperm resistance to cooling at 17 °C

The modern pig industry relies on extensive use of artificial insemination with cooled semen. It is important that semen doses maintain their quality during processing, transport and storage before insemination to guarantee maximum fertility rates. However, ejaculates may respond differently to liquid preservation at 17 °C, despite the optimal quality assessed before cooling. Thus, the aim of this study was to identify differences in seminal plasma proteome of ejaculates with a higher or lower seminal resistance to storage at 17 °C. A total of 148 ejaculates from 65 sexually mature healthy boars were classified as: High Resistance to cooling (HR, total motility > 60% at 144h) and Low resistance to cooling (LR, total motility <60 at 72h). To identify differentially expressed seminal plasma proteins between HR and LR ejaculates, ten ejaculates of each group were analyzed by 2D SDS-PAGE and ESI-Q-TOF mass spectrometry. The proteins associated with HR ejaculates were cathepsin B (spot 2803 and 6601, p < 0.01); spermadhesin PSP-I (spots 3101 and 3103, p < 0.05); epididymal secretory protein E1 precursor (spot 2101, p < 0.05) and IgGFc binding protein (spot 1603, p < 0.01). The protein associated with LR group was the Major seminal plasma PSPI (spot 9103, p < 0.01). To our knowledge, this is the first report of the association of boar seminal plasma proteins to semen resistance to cold storage at 17 °C. These results suggest the use of these proteins as biomarkers for semen resistance to preservation at 17 °C.

New insights on a NGF-mediated pathway to induce ovulation in rabbits (Oryctolagus cuniculus)

To investigate the ovulatory mechanisms triggered by raw semen (RS) in rabbits, we examined the expression of nerve growth factor (NGF)-a supposed ovulation-inducing factor (OIF)-and cognate receptors in anterior pituitary, ovary, and cervix as well as plasma NGF and luteinizing hormone (LH) concentrations. Six does/group were sham-inseminated with sterile saline (PBS), naturally mated (NM), inseminated with RS alone or after lumbar anesthesia (ARS), or treatment with COX inhibitors (CIRS). Immunohistochemistry revealed positive signals for NGF and receptors in all tissues. RT-PCR confirmed the presence of the target transcripts in the same tissues, except NTRK1 in the cervix. Circulating NGF concentrations rose 3- to 6-fold (P < 0.01) 15 min after semen deposition into the genital tract of NM, RS, and ARS rabbits and remained sustained thereafter. Circulating NGF was 4-fold lower (P < 0.01) in CIRS than in RS does indicating that NGF is mainly synthesized by the uterus. A concomitant rise of LH and NGF concentrations was found in 83.3%, 50.0%, and 16.7% of NM, RS, and CIRS does, respectively, but not in ARS (despite high NGF circulating levels). Seminal plasma NGF concentration was 151.9 ± 9.25 μg/mL. The ovulatory responses were 0%, 83.3%, 66.7%, 16.7%, and 0% in PBS, NM, RS, ARS, and CIRS groups, respectively. Present data confirm that, although RS may induce ovulation via endocrine mechanisms through binding to NGF receptors in the ovary, a novel OIF-mediated neural mechanism facilitates ovulation in rabbits.

Boar semen proteomics and sperm preservation

Recently numerous proteomic approaches have been undertaken to identify sperm and seminal plasma (SP) proteins that can be used as potential biomarkers for sperm function, including fertilization ability. This review aims firstly to briefly introduce the proteomic technologies and workflows that can be successfully applied for sperm and SP proteomic analysis. Secondly, we summarize the current knowledge about boar SP and the sperm proteome, focusing mainly on its relevance to sperm preservation procedures (liquid storage or cryopreservation) and their outcomes in terms of sperm function and fertility.

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.

Protein Fingerprinting of Seminal Plasma Reveals Dysregulation of Exosome-Associated Proteins in Infertile Men with Unilateral Varicocele

Purpose

Aberrant expression of seminal plasma proteins are associated with altered homeostasis that may affect the fertilizing ability of spermatozoa. However, the precise roles of seminal exosomes on sperm function remain unclear. The objective of this study was to identify the differentially expressed proteins (DEPs) associated with varicocele-mediated infertility by comparing seminal plasma protein profile of unilateral varicocele patients with proven fertile donors.

Materials and Methods

Semen samples were obtained from 10 proven fertile donors with normal semen parameters and 33 infertile patients with unilateral varicocele. For proteomic analysis, 5 samples from each group were pooled and run in triplicate. Key DEPs (ANXA2, TF, CD63, KIF5B, SEMG1) associated with the exosome function were selected by bioinformatic tools and validated using Western blotting.

Results

A total of 47 seminal plasma proteins were differentially expressed in unilateral varicocele patients compared to fertile donors. Validation of exosome-associated DEPs in unilateral varicocele patients (n=7) and fertile donors (n=7) revealed significant upregulation of ANXA2 (p=0.0016) and downregulation of KIF5B (p=0.009). The main upstream regulators of the DEPs in seminal plasma of unilateral varicocele group were androgen receptor, YB1 and NRF2.

Conclusions

This is the first report to identify DEPs in seminal plasma of unilateral varicocele patients compared to fertile donors. Based on the detection of DEPs associated with exosomal function, Western blotting was used to validate the presence of defective exosome machinery in seminal plasma of unilateral varicocele patients. KIF5B and ANXA2 can be utilized as potential biomarkers of infertility in unilateral varicocele patients.

Maternal protein restriction differentially alters the expression of AQP1, AQP9 and VEGFr-2 in the epididymis of rat offspring

Background: Maternal protein restriction causes sperm alterations in the offspring, most of which are associated with epididymal functions. Because fluid reabsorption/secretion dynamics in the epididymal environment play important roles in the process of sperm maturation and concentration, we investigated the effects of maternal protein restriction on the expression of aquaporins (AQP1 and AQP9), vascular endothelial growth factor (VEGFa), and its receptor VEGFr-2 in different stages of postnatal epididymal development. Methods: Pregnant rats were divided into groups that received normoprotein (17% protein) and low-protein diets (6% protein) during gestation and lactation. After weaning, male rats only received the standard diet and were euthanized at the predetermined ages of 21, 44 and 120 days. Results: Maternal protein restriction decreased AQP1 and AQP9 expression in the initial segment and caput epididymis compared to the increased expression of these proteins observed in the corpus and cauda at all ages. Although protein restriction reduced the microvasculature density (MVD) on postnatal day (PND) 21 and 44, the MVD was unaltered on PND 120. Conclusions: Maternal protein restriction changed the structure or function of the offspring’s epididymis, specifically by affecting fluid dynamics and vasculogenesis in important stages of epididymis development.

Driving the Next Generation: Paternal Lifetime Experiences Transmitted via Extracellular Vesicles and Their Small RNA Cargo

Epidemiological studies provide strong evidence for the impact of diverse paternal life experiences on offspring neurodevelopmental disease risk. While these associations are well established, the molecular mechanisms underlying these intergenerational transmissions remain elusive, though recent studies focusing on the influence of paternal experience before conception have implicated germ cell epigenetic programming. Any model accounting for the germline transfer of nongenetic information from sire to offspring must include certain components, such as 1) a vector to carry any signal from the paternal compartment to the maternal reproductive tract and future embryo; 2) a molecular signal, encoded by a paternal experience, to carry this memory and enact downstream responses; and 3) a target cell or tissue to receive the signal and convert it into an effect on embryonic development. We explore the current understanding of the potential processes and candidate factors that may serve as these components. We specifically discuss the growing appreciation for the importance of extracellular vesicles in these processes, beginning with their known role in delivering potential signals, including small RNAs, to sperm, the prototypical vector, during their posttesticular maturation. Finally, we explore the possibility that paternal extracellular vesicles could themselves serve as vectors, delivering signals not only to gametes or the zygote but also to tissues of the maternal reproductive tract to influence fetal development.

Identification of a complex population of chromatin-associated proteins in the European sea bass (Dicentrarchus labrax) sperm

A very common conception about the function of the spermatozoon is that its unique role is to transmit the paternal genome to the next generation. Most of the sperm genome is known to be condensed in many species by protamines, which are small and extremely positively charged proteins (50-70% arginine) with the functions of streamlining the sperm cell and protecting its DNA. However, more recently, it has been shown in mammals that 2-10% of its mature sperm chromatin is also associated to a complex population of histones and chromatin-associated proteins differentially distributed in the genome. These proteins are transferred to the oocyte upon fertilization and may be involved in the epigenetic marking of the paternal genome. However, little information is so far available on the additional potential sperm chromatin proteins present in other protamine-containing non-mammalian vertebrates detected through high-throughput mass spectrometry. Thus, we started the present work with the goal of characterizing the mature sperm proteome of the European sea bass, with a particular focus on the sperm chromatin, chosen as a representative of non-mammalian vertebrate protamine-containing species. Proteins were isolated by acidic extraction from purified sperm cells and from purified sperm nuclei, digested with trypsin, and subsequently the peptides were separated using liquid chromatography and identified through tandem mass spectrometry. A total of 296 proteins were identified. Of interest, the presence of 94 histones and other chromatin-associated proteins was detected, in addition to the protamines. These results provide phylogenetically strategic information, indicating that the coexistence of histones, additional chromatin proteins, and protamines in sperm is not exclusive of mammals, but is also present in other protamine-containing vertebrates. Thus, it indicates that the epigenetic marking of the sperm chromatin, first demonstrated in mammals, could be more fundamental and conserved than previously thought. Abbreviations: AU-PAGE: acetic acid-urea polyacrylamide gel electrophoresis; CPC: chromosomal passenger complex; DTT: dithiothreitol; EGA: embryonic genome activation; FDR: false discovery rate; GO: Gene Ontology; IAA: iodoacetamide; LC: liquid chromatography; LC-MS/MS: liquid chromatography coupled to tandem mass spectrometry; MS: mass spectrometry; MS/MS: tandem mass spectrometry; MW: molecular weight; PAGE: polyacrylamide gel electrophoresis; PBS: phosphate buffered saline; SDS: sodium dodecyl sulfate; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; TCA: trichloroacetic acid.

Is boar sperm freezability more intrinsically linked to spermatozoa than to the surrounding seminal plasma?

This study aimed to elucidate the effect of seminal plasma (SP) from post-SRF on boar sperm freezability and, in addition, to determine the relevance of sperm itself to sustain cryopreservation, regardless of the SP surrounding them. Twelve ejaculates from three boars were manually collected in fractions/portions, P1: the first 10 mL of the SRF, P2: the rest of the SRF and the post-SRF. Immediately, samples were centrifuged to separate spermatozoa from the surrounding SP. Spermatozoa from P1 and P2 were then incubated with its own SP or that from post-SRF, diluted in BTS (1:1, v/v) at 17 °C overnight before being frozen in 0.5 mL straws using a standard protocol. Sperm motility (total and progressive) deteriorated (P < 0.05) when P1- or P2-sperm when incubated overnight in SP from post-SRF, while sperm viability differed between P1 and P2 (P < 0.05) regardless of the SP they were incubated in. Post-thaw sperm quality and functionality differed between P1 and P2, regardless of the SP used for overnight pre-freezing incubation. Post-thaw motility (P < 0.05) and viability (P < 0.01), as well as plasma membrane fluidity (P < 0.05) or lipid peroxidation values (P < 0.01) were best in P1 sperm compared to those of P2. The protein profile of sperm from P1 and P2, analyzed by 2D-PAGE, showed qualitative differences, which suggest that sperm rather than SP would explain differences in sperm freezability between ejaculate fractions/portions. Use of P1 fraction spermatozoa seems thus optimal for cryopreservation.

G protein-coupled estrogen receptor (GPER) in adult boar testes, epididymis and spermatozoa during epididymal maturation

The G protein-coupled estrogen receptor (GPER) is a transmembrane receptor considered as a mediator of rapid non-genomic responses. GPER has been found in the male reproductive tract of many mammalian species. However, in adult boars, GPER has been reported only in ejaculated spermatozoa. Therefore, we focused on GPER detection in testicular and epididymal tissues and sperm cells in adult boars. We found GPER in Leydig cells and seminiferous tubules of boar testes and in the secretory epithelium of epididymis. A weaker signal was visible in smooth muscle cells and spermatozoa in the epididymal tubule. In spermatozoa isolated from epididymal parts, GPER was found to localize mainly in the sperm acrosome and flagellum. We immunodetected several protein bands in the extracts of the tissues and epididymal spermatozoa. A significantly higher amount of GPER mRNA was detected in the spermatozoa from caput epididymis, whereas the mRNA expression was lower in tissues of testes and caput epididymal. Our results showed the first evidence of GPER in boar epididymal spermatozoa. Moreover, the GPER localization in adult boar testes, epididymis, and mature spermatozoa suggests the involvement of estrogens via transmembrane receptor and rapid non-genomic signaling in both the sperm development and post-testicular maturation.

Seminal plasma proteomes and sperm fertility

During ejaculation, the spermatozoa are transported by the seminal plasma, a fluid resulting from secretions originating mainly from the prostate and the seminal vesicles in mammals. The interaction of the seminal plasma with spermatozoa induces binding of seminal proteins onto the sperm surface and membrane remodeling potentially impacting the sperm transport, survival and fertilizing ability in the female genital tract. The seminal plasma also contains peptides and proteins involved in the inflammatory and immune response of the female tract. Therefore the seminal plasma proteome has been investigated in a large range of taxa, including mammals, birds, fishes and insect species. The association of the seminal plasma with semen preservation or fertility identified proteic markers of seminal plasma function in domestic species. This review summarizes the current knowledge in seminal plasma proteomes and proteic markers of sperm preservation in animal species.

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.

Regulation of apical blebbing in the porcine epididymis

Apical blebbing, a non-classical secretion mechanism, occurs in the mature porcine epididymis as part of its normal function. Proteins secreted by this mechanism contribute to the modification of the sperm plasma membrane during epididymal transit and are thought to contribute to acquisition of fertilizing ability. However, little is known about the regulation of this secretion mechanism in an in vivo model. Previous work demonstrated apical blebbing in the epididymis developed pubertally, suggesting androgens, sperm or other luminal factors regulated this process. Hence, the objective was to evaluate the hypothesized regulation of apical blebbing in the epididymis of pubertal boars by androgens and luminal factors. Androgen receptor blockade (flutamide) and surgical interventions (efferent duct ligation, orchidectomy or transection of the caput epididymis) were used to alter signaling, and the subsequent effects on apical blebbing were evaluated histologically. Apical blebbing was not altered by androgen receptor blockade with flutamide, but was significantly reduced 24 h after efferent duct ligation and after orchidectomy, treatments that eliminated luminal flow from the testis (P < 0.05). Like efferent duct ligation, epididymal transection altered luminal flow without removing the androgen source and significantly reduced the appearance of apical blebbing (P < 0.05). In conclusion, apical blebbing in the porcine epididymis appears to be regulated by luminal factors.

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.

Key factors enhancing sperm fertilizing ability are transferred from the epididymis to the spermatozoa via epididymosomes in the domestic cat model

PURPOSE

Spermatozoa undergo critical changes in structure and function during the epididymal transit. Our previous studies in the domestic cat demonstrated that incidence of cenexin-a key protein involved in the centrosomal maturation-progressively increases in sperm cells from caput to cauda epididymidis. The objectives of the study were to (1) characterize mechanisms involved in transferring key factors-using the cenexin as a marker-between the epididymis and maturing sperm cells and (2) demonstrate the impact of such mechanisms on the acquisition of functional properties by spermatozoa.

METHODS

Epididymides were dissected from adult cat testes to assess the presence and localization of cenexin in testicular tissues and each epididymal segment (caput, corpus, and cauda) via immunofluorescence, Western blot, and mass spectrometry.

RESULTS

Results showed that tissues, luminal fluid, and isolated epididymosomes from each segment contained cenexin. Co-incubation of immature sperm cells for 3 h with luminal fluid or epididymosomes followed by immunostaining revealed that percentages of sperm cells containing cenexin significantly increased in samples co-incubated with epididymosome suspensions. Additionally, epididymosome co-incubation with immature spermatozoa resulted in sustained motility compared to untreated spermatozoa while there was no significant effect on acrosome integrity.

CONCLUSIONS

Taken together, these results suggest that epididymosomes play a critical role in epididymal sperm maturation and could be ideal vehicles to assist in the enhancement or suppression of male fertility.

Pattern of protein expression in the epididymis of Oligoryzomys nigripes (Cricetidae, Sigmodontinae)

In the epididymis, epithelial cells work in a concerted manner to create a luminal environment for sperm maturation, transport, and storage. However, the cell functions may be affected by anthropogenic factors, causing negative impacts on male fertility. In our study, we describe the pattern of protein expression in the epithelium and luminal fluid from epididymis of Oligoryzomys nigripes, a South American sigmodontine rodent whose reproductive biology has been little studied. Nine animals were captured from a preserved area of Atlantic Forest, where the exposure to anthropogenic influences is minimal. Epididymides were processed for histological analysis under light and epifluorescence microscopy, in which we used cell-specific markers aquaporin 9 (AQP9), vacuolar H⁺-ATPase (V-ATPase), and cytokeratin 5 (KRT5). Other samples were assessed for protein expression using shotgun proteomics. Similar to laboratory rodents, principal cells expressed AQP9 in their stereocilia. Basal cells, identified by KRT5 labeling, presented lateral body projections and a few axiopodia going toward the lumen. Clear cells expressed V-ATPase in their sub-apical vesicles and microplicae, and showed different shapes along the duct. Shotgun proteomics detected 51 proteins from epididymal supernatant. Most of them have been previously described in other species, indicating that they are well conserved. Twenty-three proteins detected in O. nigripes have not been described in epididymis from other South American sigmodontine rodents, confirming that the secretion pattern is species-specific. Our findings in O. nigripes from a protected area may help to create a baseline for studies investigating the effects of anthropogenic factors on functionality of the epididymal epithelium.

Epididymal α-l-fucosidase and its possible role in remodelling the surface of bull spermatozoa

The mammalian epididymis provides an appropriate environment for sperm maturation. During the epididymal transit, spermatozoa undergo biochemical and morphological changes that lead to the acquisition of the fertilizing capacity. In this study we analysed the fucosylation status of membrane glycoproteins in the spermatozoa obtained from different regions of the bull epididymis. High amounts of fucose were detected on caput spermatozoa (R.F.I. = 1010 ± 20.35), mostly located in the post-acrosome zone. A significant decrease in the fucose levels was detected toward the cauda (R.F.I. = 540.5 ± 49.93) (P < 0.05). This decrease was in line with the increased activity of α-l-fucosidase in the cauda fluid. In sperm from the cauda, the defucosylation occurred in some proteins, whereas others showed higher fucosylation rates. A significant decrease of fucose in the gametes was observed upon incubation of crude cauda fluid with caput spermatozoa (from R.F.I. = 1.45 ± 0.08 to 1.06 ± 0.03) (P < 0.05) indicating that the α-l-fucosidase present in the epididymal fluid is active on spermatozoa. Moreover, this effect was blocked with specific enzyme inhibitors. These results provide direct evidence that the α-l-fucosidase from epididymal fluid participates in the fucose removal from spermatozoa, as a step of sperm maturation in the bull epididymis.

Proteomic analysis of seminal plasma from locally-adapted "Curraleiro Pé-Duro bulls" (Bos taurus): identifying biomarkers involved in sperm physiology in endangered animals for conservation of biodiversity

The present study was aimed at evaluating the seminal plasma proteins and sperm parameters of Curraleiro Pé-Duro bulls. Semen was collected from 10 bulls by electroejaculation, and sperm parameters were evaluated in fresh and frozen-thawed semen. Seminal plasma proteins were analyzed by 2-D SDS-PAGE and mass spectrophotometry. Tools in computational biology were used to generate bioinformatic knowledge and evaluate gene ontology, protein-protein interactions, phylogenetic trees and multiple sequence alignments. Sperm motility in fresh and frozen-thawed semen was 78.8±1.8% and 21.2±1.6%, respectively. Pearson's correlations were evaluated (p<0.05). Sperm motility and vigor in fresh semen were correlated with clusterin, TIMP2 and cathepsin S (r=0.64-0.71) and sperm defects were related to inhibitor of carbonic anhydrase and BSP 5 (r=0.78-0.80). Clusterin, BSP 5, alpha-enolase, creatine kinase M-type, glyceraldehyde-3-phosphate dehydrogenase, BSP 3, albumin, and 5'-nucleotidase and legumain were correlated with acrosome intact live sperm (r=0.80-0.64). Associations were detected between sperm vigor and spermadhesin 1 (r=-0.89), and between sperm defects in fresh semen and spermadhesin 1 and clusterin (r=-0.81). Sperm motility in frozen-thawed semen was associated with BSP 1, spermadhesin 1, clusterin and spermadhesin Z13 (r=0.64-0.85). The percent of motile sperm after freeze-thawing was negatively correlated (r=-0.64) with the amount of spermadhesin 1 in the seminal plasma. Based on in silico analysis, TIMP2 interacted with BSP1, BSP3, BSP5 and metalloproteinases. Molecular functions of proteins associated with sperm parameters were binding, catalytic activity and enzymatic regulation. Amino acid sequences of spermadhesin 1 and BSP 1 from Bos taurus, and other domestic species were similar. Phylogenetic tree analysis demonstrated that clusterin from Bos taurus was related to Ovis aries and domains of clusterin, spermadhesin 1, BSP 1 and inhibitor of carbonic anhydrase were conserved as well. In summary, specific seminal proteins are associated with sperm parameters of locally-adapted bulls. Use of the endangered mammalian as a model may assist in understanding aspects of evolutionary adaptations and could improve assisted reproductive biotechnologies.

Proteomic analysis of mature and immature ejaculated spermatozoa from fertile men

Dysfunctional spermatozoa maturation is the main reason for the decrease in sperm motility and morphology in infertile men. Ejaculated spermatozoa from healthy fertile men were separated into four fractions using three-layer density gradient. Proteins were extracted and bands were digested on a LTQ-Orbitrap Elite hybrid mass spectrometer system. Functional annotations of proteins were obtained using bioinformatics tools and pathway databases. Western blotting was performed to verify the expression levels of the proteins of interest. 1469 proteins were identified in four fractions of spermatozoa. The number of detected proteins decreased according to the maturation level of spermatozoa. During spermatozoa maturation, proteins involved in gamete generation, cell motility, energy metabolism and oxidative phosphorylation processes showed increasing expression levels and those involved in protein biosynthesis, protein transport, protein ubiquitination, and response to oxidative stress processes showed decreasing expression levels. We validated four proteins (HSP 70 1A, clusterin, tektin 2 and tektin 3) by Western blotting. The study shows protein markers that may provide insight into the ejaculated spermatozoa proteins in different stages of sperm maturation that may be altered or modified in infertile men.

Extracellular vesicles in blood, milk and body fluids of the female and male urogenital tract and with special regard to reproduction

Extracellular vesicles (EVs) are released from almost all cells and tissues. They are able to transport substances (e.g. proteins, RNA or DNA) at higher concentrations than in their environment and may adhere in a receptor-controlled manner to specific cells or tissues in order to release their content into the respective target structure. Blood contains high concentrations of EVs mainly derived from platelets, and, at a smaller amount, from erythrocytes. The female and male reproductive tracts produce EVs which may be associated with fertility or infertility and are released into body fluids and mucosas of the urogenital organs. In this review, the currently relevant detection methods are presented and critically compared. During pregnancy, placenta-derived EVs are dynamically detectable in peripheral blood with changing profiles depending upon progress of pregnancy and different pregnancy-associated pathologies, such as preeclampsia. EVs offer novel non-invasive diagnostic tools which may reflect the situation of the placenta and the foetus. EVs in urine have the potential of reflecting urogenital diseases including cancers of the neighbouring organs. Several methods for detection, quantification and phenotyping of EVs have been established, which include electron microscopy, flow cytometry, ELISA-like methods, Western blotting and analyses based on Brownian motion. This review article summarises the current knowledge about EVs in blood and cord blood, in the different compartments of the male and female reproductive tracts, in trophoblast cells from normal and pre-eclamptic pregnancies, in placenta ex vivo perfusate, in the amniotic fluid, and in breast milk, as well as their potential effects on natural killer cells as possible targets.