Proteomics of semen and its constituents

Metabolomics of male infertility

This review explores the use of metabolomics in male infertility. Metabolomics, an evolving omics technology that targets the products of cellular metabolism, is valuable for elucidating underlying pathophysiology of many disorders including male infertility. The identification of reliable biomarkers is essential for accurate diagnosis and for developing precision therapeutics for those afflicted by reproductive dysfunction. Unfortunately, despite significant progress to date, the intricate relationships between these metabolic pathways and male infertility remain elusive. It is clear, however, that additional research is required to more fully characterize the role of metabolomics in this disorder and in the potential development of targeted therapies for precision medicine.

The Application of Ejaculate-Based Shotgun Proteomics for Male Infertility Screening

Problems with the male reproductive system are of both medical and social significance. As a rule, spermatozoa and seminal plasma proteomes are investigated separately to assess sperm quality. The current study aimed to compare ejaculate proteomes with spermatozoa and seminal plasma protein profiles regarding the identification of proteins related to fertility scores. A total of 1779, 715, and 2163 proteins were identified in the ejaculate, seminal plasma, and spermatozoa, respectively. Among these datasets, 472 proteins were shared. GO enrichment analysis of the common proteins enabled us to distinguish biological processes such as single fertilization (GO:0007338), spermatid development (GO:0007286), and cell motility (GO:0048870). Among the abundant terms for GO cellular components, zona pellucida receptor complex, sperm fibrous sheath, and outer dense fiber were revealed. Overall, we identified 139 testis-specific proteins. For these proteins, PPI networks that are common in ejaculate, spermatozoa, and seminal plasma were related to the following GO biological processes: cilium movement (GO:0003341), microtubule-based movement (GO:0007018), and sperm motility (GO:0097722). For ejaculate and spermatozoa, they shared 15 common testis-specific proteins with spermatogenesis (GO:0007283) and male gamete generation (GO:0048232). Therefore, we speculated that ejaculate-based proteomics could yield new insights into the peculiar reproductive physiology and spermatozoa function of men and potentially serve as an explanation for male infertility screening.

Seminal plasma modulates post-thaw longevity and motility of frozen sperm in dromedary camel

OBJECTIVE

This study investigated the effect of adding seminal plasma to frozen-thawed semen on the quality of sperm and pregnancy following insemination in dromedary camels.

METHODS

In experiment 1, the frozen-thawed semen from 9 collections (3 bulls) was further diluted with either the base extender or homologous seminal plasma (HSP). In the second experiment, a pooled sample of frozen-thawed semen was diluted with either seminal plasma from another three bulls. Live percentage, total and progressive motility, functional and acrosome integrity, and sperm kinematics were evaluated at 15, 60, and 120 minutes post-thawing and compared to the non-treated control. In experiment 3, frozen semen was used to inseminate camels in the following experimental groups: 1-Single insemination with double dose undiluted frozen semen (n = 9); 2-Re-insemination in 6 hours with undiluted semen (n = 13); 3-Single insemination with HSP treated sperm (n = 14).

RESULTS

Frozen-thawed sperm diluted in HSP or the non-homologous seminal plasma from Bull C indicated an improvement in all parameters after 1 hour post-thawing incubation (p<0.05). The proportion of total and progressively motile sperm did not drop significantly at 60 minutes post-thawing when diluted with the seminal plasma of Bull C (p>0.05). Double insemination with nontreated sperm and single insemination with HSP-treated sperm resulted in similar pregnancy rates (15.3% vs 21.4%, p>0.05). None of the camels conceived with double-dose single insemination of nontreated sperm.

CONCLUSION

Seminal plasma improves sperm longevity and motility after thawing in dromedary camel with a significant between-bull variation in effect. Low post-thaw sperm longevity might be the cause behind the low pregnancy rates in frozen semen insemination of dromedary camels.

Immune Regulation of Seminal Plasma on the Endometrial Microenvironment: Physiological and Pathological Conditions

Seminal plasma (SP) accounts for more than 90% of semen volume. It induces inflammation, regulates immune tolerance, and facilitates embryonic development and implantation in the female reproductive tract. In the physiological state, SP promotes endometrial decidualization and causes changes in immune cells such as macrophages, natural killer cells, regulatory T cells, and dendritic cells. This leads to the secretion of cytokines and chemokines and also results in the alteration of miRNA profiles and the expression of genes related to endometrial tolerance and angiogenesis. Together, these changes modulate the endometrial immune microenvironment and contribute to implantation and pregnancy. However, in pathological situations, abnormal alterations in SP due to advanced age or poor diet in men can interfere with a woman's immune adaptation to pregnancy, negatively affecting embryo implantation and even the health of the offspring. Uterine pathologies such as endometriosis and endometritis can cause the endometrium to respond negatively to SP, which can further contribute to pathological progress and interfere with conception. The research on the mechanism of SP in the endometrium is conducive to the development of new targets for intervention to improve reproductive outcomes and may also provide new ideas for semen-assisted treatment of clinical infertility.

Exploring the internal exposome of seminal plasma with semen quality and live birth: A Pilot Study

Infertility is clinically defined as the inability to achieve pregnancy within 12 months of regular unprotected sexual intercourse and affects 15% of couples worldwide. Therefore, the identification of novel biomarkers that can accurately predict male reproductive health and couples' reproductive success is of major public health significance. The objective of this pilot study is to test whether untargeted metabolomics is capable of discriminating reproductive outcomes and understand associations between the internal exposome of seminal plasma and the reproductive outcomes of semen quality and live birth among ten participants undergoing assisted reproductive technology (ART) in Springfield, MA. We hypothesize that seminal plasma offers a novel biological matrix by which untargeted metabolomics is able to discern male reproductive status and predict reproductive success. The internal exposome data was acquired using UHPLC-HR-MS on randomized seminal plasma samples at UNC at Chapel Hill. Unsupervised and supervised multivariate analyses were used to visualize the differentiation of phenotypic groups classified by men with normal or low semen quality based on World Health Organization guidelines as well as by successful ART: live birth or no live birth. Over 100 exogenous metabolites, including environmentally relevant metabolites, ingested food components, drugs and medications, and metabolites relevant to microbiome-xenobiotic interaction, were identified and annotated from the seminal plasma samples, through matching against the NC HHEAR hub in-house experimental standard library. Pathway enrichment analysis indicated that fatty acid biosynthesis and metabolism, vitamin A metabolism, and histidine metabolism were associated sperm quality; while pathways involving vitamin A metabolism, C21-steroid hormone biosynthesis and metabolism, arachidonic acid metabolism, and Omega-3 fatty acid metabolism distinguished live birth groups. Taken together, these pilot results suggest that seminal plasma is a novel matrix to study the influence of the internal exposome on reproductive health outcomes. Future research aims to increase the sample size to validate these findings.

Mapping the human sperm proteome - novel insights into reproductive research

INTRODUCTION

Spermatozoa are highly specialized cells with unique morphology. In addition, spermatozoa lose a considerable amount of cytoplasm during spermiogenesis, when they also compact their DNA, resulting in a transcriptionally quiescent cell. Throughout the male reproductive tract, sperm will acquire proteins that enable them to interact with the female reproductive tract. After ejaculation, proteins undergo post-translational modifications for sperm to capacitate, hyperactivate and fertilize the oocyte. Many proteins have been identified as predictors of male infertility, and also investigated in diseases that compromise reproductive potential.

AREAS COVERED

In this review we proposed to summarize the recent findings about the sperm proteome and how they affect sperm structure, function, and fertility. A literature search was performed using PubMed and Google Scholar databases within the past 5 years until August 2022.

EXPERT OPINION

Sperm function depends on protein abundance, conformation, and PTMs; understanding the sperm proteome may help to identify pathways essential to fertility, even making it possible to unravel the mechanisms involved in idiopathic infertility. In addition, proteomics evaluation offers knowledge regarding alterations that compromise the male reproductive potential.

Mass Spectrometry-Based Untargeted Approaches to Reveal Diagnostic Signatures of Male Infertility in Seminal Plasma: A New Laboratory Perspective for the Clinical Management of Infertility?

Male infertility has been recognized as a global health problem. Semen analysis, although considered the golden standard, may not provide a confident male infertility diagnosis alone. Hence, there is the urgent request for an innovative and reliable platform to detect biomarkers of infertility. The rapid expansion of mass spectrometry (MS) technology in the field of the 'omics' disciplines, has incredibly proved the great potential of MS-based diagnostic tests to revolutionize the future of pathology, microbiology and laboratory medicine. Despite the increasing success in the microbiology area, MS-biomarkers of male infertility currently remain a proteomic challenge. In order to address this issue, this review encompasses proteomics investigations by untargeted approaches with a special focus on experimental designs and strategies (bottom-up and top-down) for seminal fluid proteome profiling. The studies reported here witness the efforts of the scientific community to address these investigations aimed at the discovery of MS-biomarkers of male infertility. Proteomics untargeted approaches, depending on the study design, might provide a great plethora of biomarkers not only for a male infertility diagnosis, but also to address a new MS-biomarkers classification of infertility subtypes. From the early detection to the evaluation of infertility grade, new MS-derived biomarkers might also predict long-term outcomes and clinical management of infertility.

The Association between Clusterin Sialylation Degree and Levels of Oxidative–Antioxidant Balance Markers in Seminal Plasmas and Blood Sera of Male Partners with Abnormal Sperm Parameters

Nearly 30% of infertility cases are caused by male factor. This study aimed at checking the associations between the sialylation degree of glycoprotein clusterin (CLU) and levels of oxidative–antioxidant balance markers in infertile men. Using lectin-ELISA with biotinylated lectins specific to α2,6-linked (Sambucus nigra agglutinin, SNA) and α2,3-linked (Maackia amurensis agglutinin, MAA) sialic acid (SA), the CLU sialylation in 132 seminal plasmas (SP) and 91 blood sera (BS) were analyzed. Oxidative–antioxidant status was measured by determining Sirtuin-3 (SIRT3), Sirtuin-5 (SIRT5), total antioxidant status (TAS), and ferric reducing antioxidant power (FRAP) levels. We indicate that multiple sperm disorders are associated with decreased expression of MAA-reactive SA in SP. Decreased SP SIRT3 concentrations may be associated with teratozoospermia and oligoasthenoteratozoospermia. ROC curve and cluster analysis revealed that SP relative reactivity of CLU glycans with MAA, the value of MAA/SNA ratio, and SIRT3 and SIRT5 concentrations may constitute an additional set of markers differentiating infertile oligoasthenoteratozoospermic patients (OAT) from normozoospermic (N), asthenoteratozoospermic (AT) and teratozoospermic (T). The multinomial logistic regression analysis confirmed the potential utility of SIRT3 determinations for differentiation between N and OAT groups as well as between N and T groups for SIRT3 and SIRT5. For BS, based on ROC curve and cluster analysis, relative reactivities of CLU glycans with SNA, MAA, SIRT3 and FRAP concentrations may be useful in the differentiation of normozoospermic patients from those with sperm disorders. The multinomial logistic regression analysis showed that the SNA relative reactivity with CLU glycans significantly differentiated the N group from AT, OAT and T groups, and FRAP concentrations significantly differed between N and AT groups, which additionally confirms the potential utility of these biomarkers in the differentiation of infertile patients with abnormal sperm parameters. The knowledge about associations between examined parameters may also influence future research aimed at seeking new male infertility therapies.

Metabolite interactions in prostatic fluid mimics assessed by 1H NMR

INTRODUCTION

Molecular interactions in prostatic fluid are of biological interest and may affect MRI and MRS of the prostate. We investigated the existence of interactions between the major components of this fluid: spermine, citrate and myoinositol, metal ions, including zinc, and proteins.

MATERIALS AND METHODS

Solutions of 90 mM citrate, 18 mM spermine and 6 mM myo-inositol, mimicking expressed prostatic fluid, were investigated by 1H NMR using changes in T2 relaxation and chemical shift as markers for interactions.

RESULTS AND DISCUSSION

Adding to this metabolite mixture the ions Na⁺ , K⁺, Ca⁺⁺, Mg⁺⁺ and Zn⁺⁺, decreased the T2 relaxation times of citrate and spermine protons by factors of 3 and 2, respectively, with Zn++ causing the largest effect, indicating ion-metabolite interactions. The T2 of 18 mM spermine dropped by a factor of 2 upon addition with 90 mM citrate, but no effect on T2 was seen with myo-inositol pointing to a specific citrate-spermine interaction. Moreover, the T2 of citrate in the presence of spermine decreased by adding metal ions and increasing amounts of Zn⁺⁺, indicating complexation of citrate and spermine with metal ions, particularly with Zn. The addition of bovine serum albumin (BSA), as an index protein, substantially further decreased the T2 of spermine and citrate implying the formation of a transient spermine-metal ion-citrate-BSA complex. Finally, we found that the T2 of citrate in extracellular fluid of prostate cancer cells, as a mimic of fluid in cancerous prostates, decreased by adding fetal calf serum, indicating protein binding.

Effect of Anserine and Carnosine on Sperm Motility in the Japanese Quail

Sperm motility is considered as one of the most important traits for successful fertilization, but the motility of an ejaculated sperm decreases with time when stored as liquid. It is reported that seminal plasma serves as a nutrient rich medium for sperm and plays an important role in sperm motility and its fertilization ability. Several studies have reported that imidazole dipeptides such as anserine and carnosine affect sperm motility and its fertilization ability in mammals. In this study, we report the presence of anserine and carnosine in the male reproductive tract of the Japanese quail. Abundant levels of anserine (44.46 µM) and carnosine (41.75 µM) were detected in the testicular fluid and seminal plasma respectively using the amino acid analyzer; however, seminal plasma solely contained carnosine. When the ejaculates were incubated with anserine or carnosine, we found that both the dipeptides improve sperm motility parameters such as straight line velocity, curvilinear velocity, average path velocity and amplitude of lateral head displacement after in vitro sperm storage at 15°C. These results indicate that imidazole dipeptides are present in the male reproductive tract and may improve sperm quality during in vitro sperm storage in the liquid states.

The possible association of clusterin fucosylation changes with male fertility disorders

In the seminal plasma (n = 118) and serum (n = 90) clusterin (CLU) the fucosylation and the expression of selected fucosyltransferases (FUTs) were analyzed. Samples from infertile men were divided into groups based on the results of the standard semen analysis: normozoospermic (N), teratozoospermic (T), asthenoteratozoospermic (AT) and oligoasthenoteratozoospermic (OAT). The CLU fucosylation was analyzed using lectin-ELISAs with biotinylated lectins specific to α1,3-, α1,2-linked antennary fucose, and α1,6-linked core fucose (LTA, UEA, and LCA, respectively). The concentrations of FUT3 and FUT4, reflecting the expression of Le oligosaccharide structures, were measured using ELISA tests. The differences in serum CLU and FUT4 concentrations, and in the expression of core fucose and antennary fucose α1,2-linked in CLU glycans between the N group and other groups examined suggest that the disturbances in sperm count, motility, and morphology are not the only cause of male infertility. Lack of similarities between levels of examined parameters in blood serum and seminal plasma may suggest the differences in mechanisms leading to glycoproteins glycosylation. It confirmed the observed differences in concentrations of seminal plasma CLU, FUT3, and FUT4 between the OAT group and N, T, AT groups, indicating that decreased sperm count may be related to these parameters expression. The serum CLU concentrations and expression of core fucose and fucose α1,2-linked in CLU, seem to be good markers differentiating normozoospermic men from those with abnormal sperm parameters, which was not observed for seminal plasma.

Seminal Plasma: Relevant for Fertility?

Seminal plasma (SP), the non-cellular component of semen, is a heterogeneous composite fluid built by secretions of the testis, the epididymis and the accessory sexual glands. Its composition, despite species-specific anatomical peculiarities, consistently contains inorganic ions, specific hormones, proteins and peptides, including cytokines and enzymes, cholesterol, DNA and RNA-the latter often protected within epididymis- or prostate-derived extracellular vesicles. It is beyond question that the SP participates in diverse aspects of sperm function pre-fertilization events. The SP also interacts with the various compartments of the tubular genital tract, triggering changes in gene function that prepares for an eventual successful pregnancy; thus, it ultimately modulates fertility. Despite these concepts, it is imperative to remember that SP-free spermatozoa (epididymal or washed ejaculated) are still fertile, so this review shall focus on the differences between the in vivo roles of the SP following semen deposition in the female and those regarding additions of SP on spermatozoa handled for artificial reproduction, including cryopreservation, from artificial insemination to in vitro fertilization. This review attempts, including our own results on model animal species, to critically summarize the current knowledge of the reproductive roles played by SP components, particularly in our own species, which is increasingly affected by infertility. The ultimate goal is to reconcile the delicate balance between the SP molecular concentration and their concerted effects after temporal exposure in vivo. We aim to appraise the functions of the SP components, their relevance as diagnostic biomarkers and their value as eventual additives to refine reproductive strategies, including biotechnologies, in livestock models and humans.

Viruses in the reproductive tract: On their way to the germ line?

Studies of vertebrate genomes have indicated that all species contain in their chromosomes stretches of DNA with sequence similarity to viral genomes. How such 'endogenous' viral elements (EVEs) ended up in host genomes is usually explained in general terms such as 'they entered the germ line at some point during evolution'. This seems a correct statement, but is also rather imprecise. The vast number of endogenous viral sequences suggest that common routes to the 'germ line' may exist, as relying on chance alone may not easily explain the abundance of EVEs in modern mammalian genomes. An increasing number of virus types have been detected in human semen and a growing number of studies have reported on viral infections that cause male infertility or subfertility and on viral infections that threaten in vitro fertilisation practices. Thus, it is timely to survey the pathway(s) that viruses can use to gain access to the human germ line. Embryo transfer and semen quality studies in livestock form another source of relevant information because virus infection during reproduction is clearly unwanted, as is the case for the human situation. In this review, studies on viruses in the male and female reproductive tract and in the early embryo will be discussed to propose a plausible viral route to the mammalian germ line.

The High Content of Fructose in Human Semen Competitively Inhibits Broad and Potent Antivirals That Target High-Mannose Glycans

Semen is the primary transmission vehicle for various pathogenic viruses. Initial steps of transmission, including cell attachment and entry, likely occur in the presence of semen. However, the unstable nature of human seminal plasma and its toxic effects on cells in culture limit the ability to study in vitro virus infection and inhibition in this medium. We found that whole semen significantly reduces the potency of antibodies and microbicides that target glycans on the envelope glycoproteins (Envs) of HIV-1. The extraordinarily high concentration of the monosaccharide fructose in semen contributes significantly to the effect by competitively inhibiting the binding of ligands to α1,2-linked mannose residues on Env. Infection and inhibition in whole human seminal plasma are accurately mimicked by a stable synthetic simulant of seminal fluid that we formulated. Our findings indicate that, in addition to the protein content of biological secretions, their small-solute composition impacts the potency of antiviral microbicides and mucosal antibodies.IMPORTANCE Biological secretions allow viruses to spread between individuals. Each type of secretion has a unique composition of proteins, salts, and sugars, which can affect the infectivity potential of the virus and inhibition of this process. Here, we describe HIV-1 infection and inhibition in whole human seminal plasma and a synthetic simulant that we formulated. We discovered that the sugar fructose in semen decreases the activity of a broad and potent class of antiviral agents that target mannose sugars on the envelope protein of HIV-1. This effect of semen fructose likely reduces the efficacy of such inhibitors to prevent the sexual transmission of HIV-1. Our findings suggest that the preclinical evaluation of microbicides and vaccine-elicited antibodies will be improved by their in vitro assessment in synthetic formulations that simulate the effects of semen on HIV-1 infection and inhibition.

Future diagnostics in male infertility: genomics, epigenetics, metabolomics and proteomics

A male factor is involved in 50% of couples with infertility. Unfortunately, the etiology of male factor infertility remains classified as idiopathic in nearly 50% of cases. The semen analysis (SA) continues to be first line for the workup of male infertility, but it is an imperfect test with high variability between samples. This lack of diagnostic capability has led to the desire to develop minimally invasive tests to aid with understanding the etiology of male factor infertility. Genetic factors are known to play a role in male infertility, and much work has been done to identify the many genes involved. The study of the genes involved, the impact of epigenetic modifications, proteins and metabolites produced are attractive targets for development of biomarkers which may be used to diagnose the etiology of male infertility. This review aims to explore recent advances in these fields as they pertain to the diagnosis of male infertility.

Redox regulation & sperm function: A proteomic insight

Infertility affects nearly 15 per cent of all couples within the reproductive age worldwide, with about 50 per cent being exhibited in the male, called male factor infertility. Successful reproduction is dependent on sperm chromatin integrity. Spermatozoa are highly specialized cells that aim to transmit the paternal genomic blueprint to the oocyte. The spermatozoon is regulated by redox mechanisms during its epididymal transit to acquire fertilizing ability. While, at physiological levels, the production of reactive oxygen species (ROS) supports the spermatozoon to acquire its fertilizing ability, at high concentrations, it affects sperm function leading to infertility. Emerging proteomic technologies provide an opportunity to address these key issues that may solve many fertility-associated problems resulting from oxidative stress (OS). This review highlights the need for an efficient therapeutic approach to male infertility with the application of high-throughput OS-mediated proteomic technology, and also addresses the question as to whether targeting these altered sperm-specific proteins may help in designing an efficient and reversible male contraceptive.

Sperm and Seminal Plasma Proteomics: Molecular Changes Associated with Varicocele-Mediated Male Infertility

Male infertility is a rising problem and the etiology at the molecular level is unclear. Use of omics has provided an insight into the underlying cellular changes in the spermatozoa of infertile men. Proteomics is one the promising omics techniques for biomarker screening that can provide complete information on molecular processes associated with male infertility. Varicocele is a pressing issue in the field of male infertility and the search for an appropriate diagnostic and therapeutic biomarker is still ongoing. In this review, we discuss the reports on proteomic profiles of sperm and seminal plasma in male infertility and provide an in-depth insight into varicocele studies associated with male infertility.

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.

Update on the proteomics of male infertility: A systematic review

Objective

To assess the role of differentially expressed proteins as a resource for potential biomarker identification of infertility, as male infertility is of rising concern in reproductive medicine and evidence pertaining to its aetiology at a molecular level particularly proteomic as spermatozoa lack transcription and translation. Proteomics is considered as a major field in molecular biology to validate the target proteins in a pathophysiological state. Differential expression analysis of sperm proteins in infertile men and bioinformatics analysis offer information about their involvement in biological pathways.

Materials and methods

Literature search was performed on PubMed, Medline, and Science Direct databases using the keywords ‘sperm proteomics’ and ‘male infertility’. We also reviewed the relevant cross references of retrieved articles and included them in the review process. Articles written in any language other than English were excluded.

Results

Of 575 articles identified, preliminary screening for relevant studies eliminated 293 articles. At the next level of selection, from 282 studies only 80 articles related to male infertility condition met the selection criteria and were included in this review.

Conclusion

In this molecular era, sperm proteomics has created a platform for enhanced understanding of male reproductive physiology as a potential tool for identification of novel protein biomarkers related to sperm function in infertile men. Therefore, it is believed that proteomic biomarkers can overcome the gaps in information from conventional semen analysis that are of limited clinical utility.

The Use of Proteomics in Assisted Reproduction

Despite the explosive increase in the use of Assisted Reproductive Technologies (ART) over the last 30 years, their success rates remain suboptimal. Proteomics is a rapidly-evolving technology-driven science that has already been widely applied in the exploration of human reproduction and fertility, providing useful insights into its physiology and leading to the identification of numerous proteins that may be potential biomarkers and/or treatment targets of a successful ART pregnancy. Here we present a brief overview of the techniques used in proteomic analyses and attempt a comprehensive presentation of recent data from mass spectrometry-based proteomic studies in humans, regarding all components of ARTs, including the male and female gamete, the derived zygote and embryo, the endometrium and, finally, the ART offspring both pre- and postnatally.

Seminal biomarkers for the evaluation of male infertility

For men struggling to conceive with their partners, diagnostic tools are limited and often consist of only a standard semen analysis. This baseline test serves as a crude estimation of male fertility, leaving patients and clinicians in need of additional diagnostic biomarkers. Seminal fluid contains the highest concentration of molecules from the male reproductive glands, therefore, this review focuses on current and novel seminal biomarkers in certain male infertility scenarios, including natural fertility, differentiating azoospermia etiologies, and predicting assisted reproductive technique success. Currently available tests include antisperm antibody assays, DNA fragmentation index, sperm fluorescence in situ hybridization, and other historical sperm functional tests. The poor diagnostic ability of current assays has led to continued efforts to find more predictive biomarkers. Emerging research in the fields of genomics, epigenetics, proteomics, transcriptomics, and metabolomics holds promise for the development of novel male infertility biomarkers. Seminal protein-based assays of TEX101, ECM1, and ACRV1 are already available or under final development for clinical use. Additional panels of DNA, RNA, proteins, or metabolites are being explored as we attempt to understand the pathophysiologic processes of male infertility. Future ventures will need to continue data integration and validation for the development of clinically useful infertility biomarkers to aid in male infertility diagnosis, treatment, and counseling.

Proteomic profile of seminal plasma in adolescents and adults with treated and untreated varicocele

Varicocele, the most important treatable cause of male infertility, is present in 15% of adult males, 35% of men with primary infertility, and 80% of men with secondary infertility. On the other hand, 80% of these men will not present infertility. Therefore, there is a need to differentiate a varicocele that is exerting a deleterious effect that is treatable from a “silent” varicocele. Despite the growing evidence of the cellular effects of varicocele, its underlying molecular mechanisms are still eluding. Proteomics has become a promising area to determine the reproductive biology of semen as well as to improve diagnosis of male infertility. This review aims to discuss the state-of-art in seminal plasma proteomics in patients with varicocele to discuss the challenges in undertaking these studies, as well as the future outlook derived from the growing body of evidence on the seminal proteome.

The Role of Proteomics in Biomarker Development for Improved Patient Diagnosis and Clinical Decision Making in Prostate Cancer

Prostate Cancer (PCa) is the second most commonly diagnosed cancer in men worldwide. Although increased expression of prostate-specific antigen (PSA) is an effective indicator for the recurrence of PCa, its intended use as a screening marker for PCa is of considerable controversy. Recent research efforts in the field of PCa biomarkers have focused on the identification of tissue and fluid-based biomarkers that would be better able to stratify those individuals diagnosed with PCa who (i) might best receive no treatment (active surveillance of the disease); (ii) would benefit from existing treatments; or (iii) those who are likely to succumb to disease recurrence and/or have aggressive disease. The growing demand for better prostate cancer biomarkers has coincided with the development of improved discovery and evaluation technologies for multiplexed measurement of proteins in bio-fluids and tissues. This review aims to (i) provide an overview of these technologies as well as describe some of the candidate PCa protein biomarkers that have been discovered using them; (ii) address some of the general limitations in the clinical evaluation and validation of protein biomarkers; and (iii) make recommendations for strategies that could be adopted to improve the successful development of protein biomarkers to deliver improvements in personalized PCa patient decision making.

Effect of oral administration of Tribulus terrestris extract on semen quality and body fat index of infertile men

Male fertility can be evaluated through complete semen analysis. Plants belonging to the Tribulus genus are known for their role in enhancing sex hormone levels and semen quality. The aim of this study was to evaluate the effects of T. terrestris on semen quality and physiological parameters. Sixty-five men with abnormal semen evaluation were included in this study, in which they were prescribed with oral administration of Androsten^® (250 mg of Tribulus terrestris dried extract per capsule). Body fat percentage, lean muscle mass gain, fluctuation in steroid hormone levels and all semen parameters were analysed during the period of treatment. The results demonstrated that decrease in the percentage of body fat and increase in lean mass were significant, as well as increase in dihydrotestosterone levels. Complete semen analysis evaluated at the end of treatment showed significant enhancement in sperm concentration, motility and liquefaction time. Protodioscin, the main phytochemical agent of the Tribulus genus, acts on sertoli cells, germ cell proliferation and growth of seminiferous tubules. This component is known to convert testosterone into dihydrotestosterone, which plays important roles in male attributes. Our results indicate the therapeutic use of Tribulus terrestris by men presenting altered semen parameters, and/or undergoing infertility treatment.

Proteomic profile of seminal plasma in adolescents and adults with treated and untreated varicocele

Varicocele, the most important treatable cause of male infertility, is present in 15% of adult males, 35% of men with primary infertility, and 80% of men with secondary infertility. On the other hand, 80% of these men will not present infertility. Therefore, there is a need to differentiate a varicocele that is exerting a deleterious effect that is treatable from a "silent" varicocele. Despite the growing evidence of the cellular effects of varicocele, its underlying molecular mechanisms are still eluding. Proteomics has become a promising area to determine the reproductive biology of semen as well as to improve diagnosis of male infertility. This review aims to discuss the state-of-art in seminal plasma proteomics in patients with varicocele to discuss the challenges in undertaking these studies, as well as the future outlook derived from the growing body of evidence on the seminal proteome.

Qualitative and quantitative peptidomic and proteomic approaches to phenotyping chicken semen

Understanding of the avian male gamete biology is essential to improve the conservation of genetic resources and performance in farming. In this study, the chicken semen peptidome/proteome and the molecular phenotype related to sperm quality were investigated. Spermatozoa (SPZ) and corresponding seminal plasma (SP) from 11 males with different fertilizing capacity were analyzed using three quantitative strategies (fluid and intact cells MALDI-MS, SDS-PAGE combined to LC-MS/MS with spectral counting and XIC methods). Individual MALDI profiling in combination with top-down MS allowed to characterize specific profiles per male and to identify 16 biomolecules (e.g.VMO1, AvBD10 and AvBD9 including polymorphism). Qualitative analysis identified 1165 proteins mainly involved in oxidoreduction mechanisms, energy processes, proteolysis and protein localization. Comparative analyses between the most and the least fertile males were performed. The enzymes involved in energy metabolism, respiratory chain or oxido-reduction activity were over-represented in SPZ of the most fertile males. The SP of the most and the least fertile males differed also on many proteins (e.g. ACE, AvBD10 and AvBD9, NEL precursor, acrosin). Thus proteomic is a "phenomic molecular tool" that may help to discriminate avian males on their reproductive capacity. The data have been deposited with ProteomeXchange (identifiers PXD000287 and PXD001254).

BIOLOGICAL SIGNIFICANCE

This peptidomic and proteomic study i) characterized for the first time the semen protein composition of the main domestic avian species (Gallus gallus) by analysis of ejaculated spermatozoa and corresponding seminal plasma; ii) established a characteristic molecular phenotype distinguishing semen and males at an individual level; and iii) proposedthe first evidence of biomarkers related to fertility.

Prostasomes: extracellular vesicles from the prostate

The term 'prostasomes' is generally used to classify the extracellular vesicles (EVs) released into prostatic fluid by prostate epithelial cells. However, other epithelia within the male reproductive tract also release EVs that mix with 'true' prostasomes during semen emission or ejaculation. Prostasomes have been proposed to regulate the timing of sperm cell capacitation and induction of the acrosome reaction, as well as to stimulate sperm motility where all three are prerequisite processes for spermatozoa to attain fertilising capacity. Other proposed functions of prostasomes include interfering with the destruction of spermatozoa by immune cells within the female reproductive tract. On the other hand, it is unclear whether the distinct presumed functions are performed collectively by a single type of prostasome or by separate distinct sub-populations of EVs. Moreover, the exact molecular mechanisms through which prostasomes exert their functions have not been fully resolved. Besides their physiological functions, prostasomes produced by prostate tumour cells have been suggested to support prostate cancer spread development, and prostasomes in peripheral blood plasma may prove to be valuable biomarkers for prostate cancer.

The use of genomics, proteomics, and metabolomics in identifying biomarkers of male infertility

Although male factors account for approximately 50% of all infertility, the mechanisms underlying their origin are unknown. Currently, clinicians rely primarily on semen analyses to predict male reproductive potential and chart treatment success. Even when invasive procedures are performed, the causes of male factor infertility frequently remain elusive. Recently, the advent of new technologies has spurred the search for novel male infertility biomarkers, and the detection of genes, proteins, or metabolites unique to the infertile male holds much promise. The concept that a cost-effective, noninvasive, and accurate set of biomarkers can be identified to diagnose male factor infertility is tantalizing. This review focuses on the various methodologies used in the discovery of novel biomarkers along with their findings. Specific attention is paid to recent advances in the fields of genetics, proteomics, and metabolomics.

Identification and function of proteolysis regulators in seminal fluid

Proteins in the seminal fluid of animals with internal fertilization effect numerous responses in mated females that impact both male and female fertility. Among these proteins is the highly represented class of proteolysis regulators (proteases and their inhibitors). Though proteolysis regulators have now been identified in the seminal fluid of all animals in which proteomic studies of the seminal fluid have been conducted (as well as several other species in which they have not), a unified understanding of the importance of proteolysis to male fertilization success and other reproductive processes has not yet been achieved. In this review, we provide an overview of the identification of proteolysis regulators in the seminal fluid of humans and Drosophila melanogaster, the two species with the most comprehensively known seminal fluid proteomes. We also highlight reports demonstrating the functional significance of specific proteolysis regulators in reproductive and post-mating processes. Finally, we make broad suggestions for the direction of future research into the roles of both active seminal fluid proteolysis regulators and their inactive homologs, another significant class of seminal fluid proteins. We hope that this review aids researchers in pursuing a coordinated study of the functional significance of proteolysis regulators in semen.

Comparative analysis of human reproductive proteomes identifies candidate proteins of sperm maturation

Male reproductive proteomes provide basis for studying gene products and its involvement or regulation in sperm physiology. Here, a comparative study between these proteomes was performed to find potential proteins and functions associated with human sperm maturation. Seven reproductive proteomes associated with human sperm physiology were integrated. Gene ontology analysis were performed using DAVID and Panther tools to determine enriched functions. Total of 270 proteins overlapped between epididymal, prostatic milieu and sperm proteome were thought to be candidate proteins involved in sperm maturation, and they showed enriched functions of proteasomal protein catabolic process and protein folding. 34 epididymal milieu proteins and 274 prostatic milieu proteins were contributed to the composition of seminal fluids proteome. Literatures have confirmed the involvements in sperm maturation of many of these proteins The spatial expressions of 24 epididymal milieu proteins involved in chaperone and antioxidant activity were authenticated by real-time RT-PCR. These proteins may serve as candidate molecules for future studies of sperm maturation and male infertility.

Seminal plasma proteins: what role do they play?

PROBLEM

Semen is a heterogeneous and complex cell suspension in a protein-rich fluid with different functions, some of them well known, others still obscure.

METHOD OF STUDY

This paper reviews, comparatively, our current knowledge on the growing field of proteomics of the SP and its relevance in relation to the in vivo situation, for the sake of reproductive biology, diagnostics and treatment.

RESULTS

Ejaculated spermatozoa, primarily bathing in cauda epididymal fluid, are (in vitro) bulky, exposed to most, if not all, secretions from the accessory sexual glands. In vivo, however, not all spermatozoa are necessarily exposed to all secretions from these glands, because sperm cohorts are delivered in differential order and bathe in seminal plasma (SP) with different concentrations of constituents, including peptides and proteins. Proteins are relevant for sperm function and relate to sperm interactions with the various environments along the female genital tract towards the oocyte vestments. Specific peptides and proteins act as signals for the female immune system to modulate sperm rejection or tolerance, perhaps even influencing the relative intrinsic fertility of the male and/or couple by attaining a status of maternal tolerance towards embryo and placental development.

CONCLUSIONS

Proteins of the seminal plasma have an ample panorama of action, and some appear responsible for establishing fertility.

Molecular heterogeneity of gelatin-binding proteins from human seminal plasma

Defining the molecular characteristics of seminal plasma proteins is essential for understanding their function in physiological and pathological conditions. Starting from the predicted importance of human seminal plasma gelatin-binding proteins, comprising fibronectin (FN) and FN-related molecules, for male fertility, this study aims at gaining insight into their immuno-glycobiochemical properties. Human seminal plasma from subjects with normal semen parameters were separated on a gelatin-Sepharose column and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting using antibodies against distinct FN forms. Heterogeneity of the isolated molecular species was examined by protein chip arrays combined with surface-enhanced laser desorption/ionization time of flight mass spectrometry, on normal, metal and hydrophobic surfaces. Carbohydrate composition was investigated using mannose-, fucose- and sialic acid-specific plant lectins and galectin-1. The results obtained indicated a pattern of isolated proteins corresponding to that of known FN fragments, as confirmed by immunoreactivity. Among them heparin-binding ability was preferentially associated with low molecular mass species. As for posttranslational modifications, phosphorylation and glycosylation of distinct fragments were revealed. Lectin binding to fragments containing the gelatin-binding domain, particularly with Ricinus communis agglutinin I, was stronger than to fragments containing the cell-binding site of FN. A low level of sialylation and distinctive concanavalin A- and Lens culinaris agglutinin-reactive species were also observed. Galectin-1 did not interact with the isolated preparation. Resolving the molecular heterogeneity of normal human seminal plasma FN and gaining initial insight into possible similarities/differences with known FN molecular species may be considered a prerequisite step preceding challenging the clinical usefulness of these molecular properties.