Seminal plasma proteins as modulators of the sperm function and their application in sperm biotechnologies

Selection and direct biomarkers of reproductive capacity of breeding boars

Efficient management of pig reproduction is paramount for the sustainability and productivity of the global pork industry. Modern artificial insemination (AI) breeding programs have greatly benefited from the integration of advanced selection methods and biomarkers to enhance the reproductive performance of boars. While traditional selection methods have relied soley on boar phenotype, such as growth rate and conformation, modern pig breeding has shifted more and more toward molecular and genetic tools, which are still complemented by phenotypic traits. These methods encompass genomics, transcriptomics, and proteomics. Biomarkers serve as critical indicators of boar reproductive capacity. They can help to identify individuals with superior fertility and aid in the early identification of potential fertility issues, allowing for proactive management strategies. This review summarizes current knowledge of various biomarkers associated with semen quality, sperm function, and overall reproductive fitness in boars. Furthermore, we explore advanced technologies and their potential applications in uncovering novel selection methods and biomarkers for predicting boar fertility. A comprehensive understanding of selection criteria and biomarkers governing boar reproductive capacity is essential for developing effective breeding programs to enhance swine reproductive performance.

Immunological defense mechanisms of ejaculates and the spread of viral infectious diseases through pig semen

This review focuses on the mechanisms of immune tolerance and antimicrobial defense in the male genital tract of the pig. Sperm cells are foreign to the immune system and, therefore, they must be protected from the immune system. The blood-testis-barrier is mediated by a physical barrier between adjacent Sertoli cells, several cell types within the testis, and interactions between immunomodulatory molecules. The blood-epididymal-barrier is composed of a physical barrier that is lined with principal cells having a network of junctional complexes in their apical lateral membrane and completed by specific transporters. The seminal plasma (SP) contains many signaling agents involved in establishing a state of immune tolerance in the female genital tract, which is essential for successful fertilization. Specific SP-proteins, however, also have pro-inflammatory capacities contributing to transient uterine inflammation, supporting the removal of foreign cells, possible pathogens, and excessive spermatozoa. While many different proteins and other substances present in semen can damage sperm cells, they may also protect them against viral infections. A delicate balance of these substances, therefore, needs to be maintained. Related to this, recent studies have shown the importance of extracellular vesicles (EVs), as they contain these substances and convey immune signals. Yet, viruses may use EVs to interact with the male genital tract and circumvent immune responses. For this reason, further research needs to explore the role of EVs in the male reproductive tract, as it might contribute to elucidating the pathogenesis of viral infections that might be transmitted via semen and to developing better vaccines.

Proteomic Analysis of Differences in the Freezability of Porcine Sperm Identifies α-Amylase As a Key Protein

To investigate the mechanisms underlying the differences in the freezability of boar semen, Yorkshire boars with freezing-tolerant semen (YT, n = 3), Yorkshire boars with freezing-sensitive semen (YS, n = 3), Landrace boars with freezing-tolerant semen (LT, n = 3), and Landrace boars with freezing-sensitive semen (LS, n = 3) were selected for this study. Their sperm was subjected to protein extraction, followed by data-independent acquisition proteomics and functional bioinformatics analysis. A total of 3042 proteins were identified, of which 2810 were quantified. Some key KEGG pathways were enriched, such as starch and sucrose metabolism, carbohydrate digestion and absorption, mineral absorption, the HIF-1 signaling pathway, and the necroptosis pathways. Through PRM verification, we found that several proteins, such as α-amylase and epididymal sperm-binding protein 1, can be used as molecular markers of the freezing resistance of boar semen. Furthermore, we found that the addition of α-amylase to cryoprotective extender could significantly improve the post-thaw motility and quality of boar semen. In summary, this study revealed some molecular markers and potential molecular pathways contributing to the high or low freezability of boar sperm, identifying α-amylase as a key protein. This study is valuable for optimizing boar semen cryopreservation technology.

The effects of boar seminal plasma extracellular vesicles on sperm fertility

Extracellular vesicles (EVs) are abundant in body fluid and are critical in cell interaction. Seminal plasma contains numerous EVs which affecting sperm function via transferring regulatory cargoes to the sperm. However, the mechanism of seminal plasma extracellular vesicles (SP-EVs) is still not clear. The present study aimed to isolate the boar SP-EVs and explore its potential function, then identify the key protein involved in SP-EVs and sperms interaction, and elucidate mechanism of SP-EVs protein on sperms. Here, we successfully isolated and concentrated boar SP-EVs, the SP-EVs showed a typical vesicle structure under transmission electron microscopy, most of their diameters range between 50 and 200 nm and express EVs biomarkers CD9 and CD63. We proved that SP-EVs could inhibit sperm acrosome reaction and in vitro fertility. Through a data-independent acquisition analysis of protein profiles of noncapacitated sperms, normal capacitated sperms and SP-EVs treated capacitated sperms, we identified that EZRIN was one of the active proteins that participated in SP-EVs and sperms interaction. Furthermore, we tested that the inhibition of EZRIN could promote boar sperm fertility, which is in consistence with the function of SP-EVs. The results may facilitate future research of SP-EVs on sperm function and male infertility.

Impact of inclusion of post-spermatic ejaculate fraction in boar seminal doses on sperm metabolism, quality, and interaction with uterine fluid

Boar ejaculate is composed of sperm cells and seminal plasma (SP) and is emitted in different fractions (pre-sperm fraction; spermatic-rich fraction; intermediate fraction; post-spermatic fraction), with different composition of SP and volume, which could influence the sperm quality during seminal doses preparation, conservation, and interaction with the female reproductive tract. In artificial insemination (AI) centers, seminal doses are usually prepared with the spermatic-rich and intermediate fractions, but the inclusion of other ejaculate fractions, although controversial, is beginning to be applied. The objective was to evaluate the synergic effect of accumulative ejaculated fractions on sperm functionality during seminal doses preparation, throughout storage and after incubation with uterine fluid (UF). For this purpose, a total of 57 ejaculates were collected, and the following experimental groups were prepared (n = 19 per group): (F1) spermatic-rich fraction; (F2) F1 plus intermediate fraction; (F3) F2 plus post-spermatic fraction. Each group was stored for 5 days at ∼16 °C, and the following parameters were evaluated: sperm metabolism of pure and diluted semen (day 1), sperm quality parameters (days 1, 3, 5), thermal-resistance test (TRT) and incubation with uterine fluid (UF) (day 5). Sperm metabolic rates between accumulative ejaculate fractions from pure and diluted semen did not show differences. Also, sperm quality parameters were not affected by the ejaculate fraction during storage. However, sperm subjected to TRT showed similar results except for progressive motility, which was better in F2 and F3 than F1. When sperm were incubated with UF, the quality decreased in each group, but sperm from F2 and F3 were less affected than those from F1. In conclusion, the post-spermatic fraction can be included in seminal doses for their use in AI-centers, with functionality of sperm of different SP origins not being impaired throughout the storage, and responding better to thermal and UF stress. However, further research in AI-centers is necessary to test the sperm behaviour under presented conditions.

Review: Sperm cryopreservation in wild small ruminants: morphometric, endocrine and molecular basis of cryoresistance

Reproductive technologies can help to protect wild ruminant species from becoming extinct. In addition, the decline in some wild game species has also raised interest in reproductive technologies to increase the number of animals that can be produced. Most biobanking efforts have focused on developing effective protocols for preserving sperm, oocytes, and embryos. Cryopreservation of sperm remains the least invasive method and the cheapest procedure for germplasm storage. Over the last few years, several reproductive biotechnologies have been developed beyond the conventional freezing of spermatozoa. These include ultra-rapid freezing techniques. Nevertheless, fertility results after artificial insemination using frozen-thawed spermatozoa are not always acceptable in wild small ruminants. Moreover, these technological efforts have met variable success related to the sample's origin (epididymal retrieved postmortem or ejaculated) and the season of sperm sample collection and storage. Epididymal sperm shows higher cryoresistance than ejaculated sperm. Changes in sperm proteome between epididymal and ejaculated sperm seem to contribute to this different cryotolerance. The role of endocrine status has been studied in some wild species to better understand the underlying mechanism of the annual variation in ruminant sperm cryoresistance. Seasonal changes in testosterone and prolactin are involved in sperm cryoresistance; sperm recovery and cryopreservation are recommended around the end of the rutting season, when good quality sperm samples can still be obtained, testosterone levels have already decreased, and prolactin concentrations remain low. The mechanisms of hormone action on sperm freezability are not well known. Still, it has been suggested that testosterone affects cell proliferation in the testis, during spermatogenesis, and membrane properties of sperm cells during their transit through the reproductive tract, which might influence their cryotolerance. Recent studies have revealed that the expression of aquaporins in the sperm cells of small wild ruminants could also be involved in the androgen-related seasonal variation of sperm cryoresistance. Along with epididymal and ejaculated spermatozoa, the cryopreservation of testicular tissue may provide a suitable source of male gametes, becoming an alternative for establishing germplasm banks when semen cannot be collected for whatever reason.

Empirical comparison and recent advances of computational prediction of hormone binding proteins using machine learning methods

Hormone binding proteins (HBPs) belong to the group of soluble carrier proteins. These proteins selectively and non-covalently interact with hormones and promote growth hormone signaling in human and other animals. The HBPs are useful in many medical and commercial fields. Thus, the identification of HBPs is very important because it can help to discover more details about hormone binding proteins. Meanwhile, the experimental methods are time-consuming and expensive for hormone binding proteins recognition. Computational prediction methods have played significant roles in the correct recognition of hormone binding proteins with the use of sequence information and ML algorithms. In this review, we compared and assessed the implementation of ML-based tools in recognition of HBPs in a unique way. We hope that this study will give enough awareness and knowledge for research on HBPs.

Morphological and Molecular Bases of Male Infertility: A Closer Look at Sperm Flagellum

Infertility is a major health problem worldwide without an effective therapy or cure. It is estimated to affect 8-12% of couples in the reproductive age group, equally affecting both genders. There is no single cause of infertility, and its knowledge is still far from complete, with about 30% of infertile couples having no cause identified (named idiopathic infertility). Among male causes of infertility, asthenozoospermia (i.e., reduced sperm motility) is one of the most observed, being estimated that more than 20% of infertile men have this condition. In recent years, many researchers have focused on possible factors leading to asthenozoospermia, revealing the existence of many cellular and molecular players. So far, more than 4000 genes are thought to be involved in sperm production and as regulators of different aspects of sperm development, maturation, and function, and all can potentially cause male infertility if mutated. In this review, we aim to give a brief overview of the typical sperm flagellum morphology and compile some of the most relevant information regarding the genetic factors involved in male infertility, with a focus on sperm immotility and on genes related to sperm flagellum development, structure, or function.

What is the relevance of seminal plasma from a functional and preservation perspective?

When preserving sperm in the liquid or cryopreserved state, seminal plasma (SP) components within ejaculates can alter fertilizing capacity of these gametes. Depending on the species or how semen is collected, volume and concentration of SP components varies considerably. The SP contains substances essential for maintenance of sperm viability and fertility; however, these components can be deleterious depending on quantity, or duration of time before there is removal of SP from sperm in semen processing. Substances that impair (e.g., BSP - bull; HSP-1 - stallion; Major seminal plasma protein PSPI - boar) or improve (e.g., spermadhesin PSP-I - boar) spermatozoa fertilizing capacity have been identified. Depending on individual males, species, and semen collection procedures, SP removal may be beneficial before preservation in the liquid or cryopreserved state. In some cases, SP that is removed can be added back to thawing extender with there being positive effects in thawed sperm and for sperm viability in the female reproductive tract. In this review article, there is a focus on different effects of SP in samples of cooled and cryopreserved semen from four domestic species (pigs, horses, cattle, and sheep) with there being emphasis on how SP modulates the function and morphology of sperm cells before, during, and after preservation in the refrigerated or cryopreserved state. The present review is part of the Festschrift in honor of Dr. Duane Garner who made major contributions to the area of focus in this manuscript as evidenced by the many times his research is cited in this manuscript.

Advances in sperm cryopreservation in farm animals: Cattle, horse, pig and sheep

Sperm cryopreservation is one of the most important procedures in the development of biotechnologies for assisted reproduction. In some farm animals, the use of cryopreserved sperm has so many benefits for which relevance has become more evident in recent decades. Values for post-thaw sperm quality, however, are variable among species and within individuals of the same species. There is no standardized methodology for each of the stages of the cryopreservation procedure (andrological examination, semen collection, dilution, centrifugation, resuspension of the pellet with the freezing medium, packaging, freezing and post-thaw sperm evaluation), which also contributes to differences among studies. Cryotolerance markers of sperm and seminal plasma (SP) have been evaluated for prediction of ejaculate freezability. In addition, in previous research, there has been a focus on supplementing cryopreservation media with different substances, such as enzymatic and non-enzymatic antioxidants. In most studies, inclusion of these substances have led to improved post-thaw sperm quality and fertilizing capacity as a result of minimizing the adverse effects on sperm structure and function. Another approach is the use of different cryoprotectants. The aim with this review article is to provide an update on sperm cryopreservation in farm animals. The main detrimental effects of cryopreservation are described, including the negative repercussion on reproductive performance. Furthermore, the potential use of molecular biomarkers to predict sperm cryotolerance is discussed, as well as the addition of substances that can mitigate the harmful impact of freezing and thawing on sperm.

The Bovine Seminal Plasma Protein PDC-109 Possesses Pan-Antiviral Activity

Mammalian seminal plasma contains a multitude of bioactive components, including lipids, glucose, mineral elements, metabolites, proteins, cytokines, and growth factors, with various functions during insemination and fertilization. The seminal plasma protein PDC-109 is one of the major soluble components of the bovine ejaculate and is crucially important for sperm motility, capacitation, and acrosome reaction. A hitherto underappreciated function of seminal plasma is its anti-microbial and antiviral activity, which may limit the sexual transmission of infectious diseases during intercourse. We have recently discovered that PDC-109 inhibits the membrane fusion activity of influenza virus particles and significantly impairs viral infections at micromolar concentrations. Here we investigated whether the antiviral activity of PDC-109 is restricted to Influenza or if other mammalian viruses are similarly affected. We focused on Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the etiological agent of the Coronavirus Disease 19 (COVID-19), thoroughly assessing PDC-109 inhibition with SARS-CoV-2 Spike (S)-pseudotyped reporter virus particles, but also live-virus infections. Consistent with our previous publications, we found significant virus inhibition, albeit accompanied by substantial cytotoxicity. However, using time-of-addition experiments we discovered a treatment regimen that enables virus suppression without affecting cell viability. We furthermore demonstrated that PDC-109 is also able to impair infections mediated by the VSV glycoprotein (VSVg), thus indicating a broad pan-antiviral activity against multiple virus species and families.

Investigation of Sperm and Seminal Plasma Candidate MicroRNAs of Bulls with Differing Fertility and In Silico Prediction of miRNA-mRNA Interaction Network of Reproductive Function

Simple Summary

The objective of this study was to identify differentially expressed (DE) sperm and seminal plasma microRNAs (miRNAs) in high- and low-fertile Holstein bulls (four bulls per group), integrate miRNAs to their target genes, and categorize target genes based on predicted biological processes. Out of 84 bovine-specific, prioritized miRNAs analyzed by RT-PCR, 30 were differentially expressed in high-fertile sperm and seminal plasma compared to low-fertile sperm and seminal plasma, respectively (p ≤ 0.05, fold regulation ≥5 magnitudes). Interestingly, expression levels of DE-miRNAs in sperm and seminal plasma followed a similar pattern. Highly scored integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular process, and pathways. Further in silico analysis revealed categorized genes may have a plausible association with pathways regulating sperm structure and function, fertilization, and embryo and placental development. In conclusion, highly DE-miRNAs in bovine sperm and seminal plasma could be used as a tool for predicting reproductive functions. Since the identified miRNA-mRNA interactions were mostly based on predictions from public databases, the causal regulations of miRNA-mRNA and the underlying mechanisms require further functional characterization in future studies.

Abstract

Recent advances in high-throughput in silico techniques portray experimental data as exemplified biological networks and help us understand the role of individual proteins, interactions, and their biological functions. The objective of this study was to identify differentially expressed (DE) sperm and seminal plasma microRNAs (miRNAs) in high- and low-fertile Holstein bulls (four bulls per group), integrate miRNAs to their target genes, and categorize the target genes based on biological process predictions. Out of 84 bovine-specific, prioritized miRNAs analyzed by RT-PCR, 30 were differentially expressed in high-fertile sperm and seminal plasma compared to low-fertile sperm and seminal plasma, respectively (p ≤ 0.05, fold regulation ≥ 5 magnitudes). The expression levels of DE-miRNAs in sperm and seminal plasma followed a similar pattern. Highly scored integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular process, and pathways. Further, analysis of the categorized genes showed association with pathways regulating sperm structure and function, fertilization, and embryo and placental development. In conclusion, highly DE-miRNAs in bovine sperm and seminal plasma could be used as a tool for predicting reproductive functions. Since the identified miRNA-mRNA interactions were mostly based on predictions from public databases, the causal regulations of miRNA-mRNA and the underlying mechanisms require further functional characterization in future studies.

Seminal-Plasma-Mediated Effects on Sperm Performance in Humans

Seminal plasma (SP) plays a crucial role in reproduction and contains a large number of proteins, many of which may potentially modify sperm functionality. To evaluate the effects of SP identity and its protein composition on human sperm function, we treated the sperm of several males with either their own or multiple foreign SPs in all possible sperm–SP combinations (full-factorial design). Then we recorded sperm motility and viability in these combinations and investigated whether the sperm performance is dependent on sperm and SP identity (or their interaction). Finally, we studied whether the above-mentioned sperm traits are affected by the abundance of three SP proteins, dipeptidyl peptidase-4 (DPP4), neutral endopeptidase (NEP), and aminopeptidase N (APN). The identity of the SP donor affected sperm swimming velocity, viability, and the proportion of hyperactivated sperm, but males’ own SP was not consistently more beneficial for sperm than foreign SPs. Furthermore, we show that sperm performance is also partly affected by the interaction between sperm and SP donor. Finally, we found that DPP4 and NEP levels in SP were positively associated with sperm swimming velocity and hyperactivation. Taken together, our results highlight the importance of seminal plasma as a potential source of biomarkers for diagnostics and therapeutic interventions for male-derived infertility.

Impact of Seminal Plasma Composition on Sperm Freezability in Wild Mammals: A Review

This review was designed to summarize the most important information around seminal plasma composition and discuss its impact on the freezability of wild mammal semen samples. Seminal plasma is made up of various biochemical constituents, including ions, lipids, proteins, enzymes, and sugars, which vary between species in response to the presence and size of any relevant accessory glands. The biochemical constituents of seminal plasma may change as a result of age, individual variability, and seasonality. These constituents are responsible for supporting different functions in sperm cells, contributing to motility, acrosomal reaction, and fertilization events. A detailed understanding of seminal plasma biochemistry may help to optimize semen freezing protocols, enabling the dynamic alteration in diluents to allow for increased sperm viability rates after thawing.

Cryopreservation of dog epididymal spermatozoa by conventional freezing or ultra-rapid freezing with nonpermeable cryoprotectant

This study was aimed to assess the effectiveness of two methods for cryopreservation of dog epididymal spermatozoa, one by conventional freezing (CF) with shortening both equilibration and cooling times, and the other by ultra-rapid freezing (URF) with nonpermeable cryoprotectant. Sixty epididymides were recovered from thirty orchiectomized adult dogs and the sperm samples were retrieved by retrograde flushing using TCG-EY (tris, citric acid, glucose + 20% egg yolk) extender and then 20 pools were conformed. Each pool was divided into 2 aliquots and then cryopreserved by CF and URF methods respectively. The CF method maintained the cooled-pool samples for 2h (1h without and 1h with 5% glycerol) and then were frozen by liquid nitrogen (LN₂) vapors for 2 min. The URF method cryopreserved the cooled-pool samples using TCG-EY+250 mM sucrose, equilibrating during 30 min (5 °C) and submerging 30-μL drops directly in LN₂. The results showed that the URF method produced a lower percentage of total and progressive motilities and acrosome integrity (P < 0.05) than the CF method. However, the kinetic variables (curvilinear and straight-line velocities, straightness, linearity, wobble, amplitude of lateral head displacement, and beat-cross frequency) and plasma membrane integrity did not differ (P > 0.05) between both cryopreservation methods. Unlike the URF method, the width, area and perimeter of sperm head were reduced after the CF method (P < 0.05). In conclusion, despite the low motility achieved after the ultra-rapid freezing method, the similar values of kinetic, viability and head morphometric dimensions to those obtained after conventional freezing, suggest that ultra-rapid freezing with sucrose may be a useful alternative for the cryopreservation of canine epididymal sperm.

Assisted Reproductive Technology in Neotropical Deer: A Model Approach to Preserving Genetic Diversity

Simple Summary

Deer species in the Neotropical region have undergone a decline of their populations. Although conservation of their natural habitat is considered the best way to assist the species, the speed of occupation of these areas and the anthropic actions are so fast that the efforts are, at times, insufficient. As free-living populations decrease, there is a descent in the genetic diversity and an increase in crossbreeding between related individuals (inbreeding). Genetic diversity is essential for survival, since it enables natural selection to occur, providing adaptation and maintenance of the species. To protect the genetic diversity, it is possible to use reproductive techniques and conserve different types of cells, which can be used in the future to reestablish any alleles that have been lost by the populations.

Abstract

One of the most significant challenges in deer is the ability to maintain genetic diversity, avoiding inbreeding and sustaining population health and reproduction. Although our general knowledge of reproductive physiology is improving, it appears that the application of assisted reproductive technology (ART) will more efficiently advance wildlife conservation efforts and preserve genetic diversity. The purpose of this review is to present the most important results obtained with the use of ART in Neotropical deer. Thus, the state-of-the-art for estrus synchronization, semen technology, artificial insemination, and in vivo embryo production will be presented. In vitro embryo production (IVP) is also a biotechnology that is taking initial steps in deer. In this aspect, the approach with the proteomics of ovarian follicular fluid is being used as a tool for a better understanding of oocyte maturation. Finally, cell banks and the use of interspecific somatic cell nuclear transfer (iSCNT) as well as the use of stem cells for gametes differentiation are promising techniques.

CRISP protein expression in semen of the endangered Malayan tapir (Tapirus indicus)

The Malayan tapir is a large endangered herbivore native to South-east Asia with fewer than 2500 animals remaining in the wild. Although a small number of animals (183 animals held by 60 institutions) are managed in zoos and breeding centres, there is limited information on the fundamental reproductive biology of this species. The purpose of this present study was to evaluate the associations of reproductive protein biomarkers (CRISP2 and CRISP3) in the seminal plasma and spermatozoa with reproductive characteristics in male Malayan tapirs. Ejaculates were collected from zoo-housed animals by electroejaculation and assessed for sperm motility and quality traits. Seminal plasma and sperm pellets were analysed for CRISP protein expression by immunoblotting. The reproductive tract of a single animal was also analysed for CRISP2 and CRISP3 protein expression and localization by immunohistochemistry. Our results showed that both CRISP2 and CRISP3 are expressed in the seminal plasma and spermatozoa derived from Malayan tapirs. CRISP expression was positively correlated with semen quality, especially ejaculate volume, number of motile sperm, and acrosomal integrity. In addition, CRISP2 and CRISP3 protein expression were slightly high in males that had recently sired an offspring. The results suggest that CRISP proteins may serve as biomarkers for ejaculate quality and fertility in male Malayan tapirs. These findings may have significant implications for planning future breeding and re-introduction efforts for this species.

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.

Sperm Cryopreservation in American Flamingo (Phoenicopterus Ruber): Influence of Cryoprotectants and Seminal Plasma Removal

The American flamingo is a useful model for the development of successful semen cryopreservation procedures to be applied to threatened related species from the family Phoenicopteridae, and to permit genetic material banking. Current study sought to develop effective sperm cryopreservation protocols through examining the influences of two permeating cryoprotectants and the seminal plasma removal. During two consecutive years (April), semen samples were collected and frozen from American flamingos. In the first year, the effect of two permeating cryoprotectants, DMA (dimethylacetamide) (6%) or Me2SO (dimethylsulphoxide) (8%), on frozen-thawed sperm variables were compared in 21 males. No differences were seen between DMA and Me2SO for sperm motility, sperm viability, and DNA fragmentation after thawing. In the second year, the role of seminal plasma on sperm cryoresistance was investigated in 31 flamingos. Sperm samples were cryopreserved with and without seminal plasma, using Me2SO (8%) as a cryoprotectant. The results showed that samples with seminal plasma had higher values than samples without seminal plasma for the following sperm variables: Straight line velocity (22.40 µm/s vs. 16.64 µm/s), wobble (75.83% vs. 69.40%), (p < 0.05), linearity (62.73% vs. 52.01%) and straightness (82.38% vs. 73.79%) (p < 0.01); but acrosome integrity was lower (55.56% vs. 66.88%) (p < 0.05). The cryoresistance ratio (CR) was greater in samples frozen with seminal plasma than without seminal plasma for CR-progressive motility (138.72 vs. 54.59), CR-curvilinear velocity (105.98 vs. 89.32), CR-straight line velocity (152.77 vs. 112.58), CR-average path velocity (122.48 vs. 98.12), CR-wobble (111.75 vs. 102.04) (p < 0.05), CR-linearity (139.41 vs. 113.18), and CR-straightness (124.02 vs. 109.97) (p < 0.01). This research demonstrated that there were not differences between Me2SO and DMA to successful freezing sperm of flamingos; seminal plasma removal did not provide a benefit for sperm cryopreservation.

Tolerance of Stored Boar Spermatozoa to Autologous Seminal Plasma: A Proteomic and Lipidomic Approach

Long-term exposure of liquid preserved boar spermatozoa to seminal plasma (SP) can cause dramatic sperm injury. This study examined whether boar specificity exists in the sensitivity of spermatozoa to SP and whether correspondent biomarkers can be identified. Consecutive ejaculates (n = 4–5) collected from 19 boars were centrifuged, diluted with a pH-stablising extender with 10% (v/v) autologous SP and evaluated by computer-assisted semen analysis and flow cytometry. Up until 144 h storage, four boars showed consistently high sperm motility, viability and mitochondria activity, and one boar showed consistently low values. Intra-boar variability was high in the other boars. Screening of SP (n = 12 samples) for protein markers using mass spectrometry identified three protein candidates of which the granulin precursor, legumain and AWN were 0.5 to 0.9 log2-fold less abundant (p < 0.05) in SP-resistant compared to SP-sensitive samples. Lipidome analysis by mass spectrometry revealed 568 lipids showing no difference between the SP-groups. The most abundant lipids were cholesterol (42,442 pmol), followed by phosphatidylserine (20,956 pmol) and ether-linked phosphatidylethanolamine (13,039 pmol). In conclusion, three candidate proteins were identified which might be indicative of SP-tolerance of sperm during long-term storage. Noteworthy, a first lipidomic profile of boar SP is presented.

Effect of Seminal Plasma Protein Fractions on Stallion Sperm Cryopreservation

Seminal plasma (SP) is the natural environment for spermatozoa and contains a number of components, especially proteins important for successful sperm maturation and fertilization. Nevertheless, in standard frozen stallion insemination doses production, SP is completely removed and is replaced by a semen extender. In the present study, we analyzed the effects of the selected seminal plasma protein groups that might play an important role in reducing the detrimental effects on spermatozoa during the cryopreservation process. SP proteins were separated according to their ability to bind to heparin into heparin-binding (Hep+) and heparin-non-binding (Hep-) fractions. The addition of three concentrations-125, 250, and 500 µg/mL-of each protein fraction was tested. After thawing, the following parameters were assessed: sperm motility (by CASA), plasma membrane integrity (PI staining), and acrosomal membrane integrity (PNA staining) using flow cytometry, and capacitation status (anti-phosphotyrosine antibody) using imaging-based flow cytometry. Our results showed that SP protein fractions had a significant effect on the kinematic parameters of spermatozoa and on a proportion of their subpopulations. The 125 µg/mL of Hep+ protein fraction resulted in increased linearity (LIN) and straightness (STR), moreover, with the highest values of sperm velocities (VAP, VSL), also this group contained the highest proportion of the fast sperm subpopulation. In contrast, the highest percentage of slow subpopulation was in the groups with 500 µg/mL of Hep+ fraction and 250 µg/mL of Hep- fraction. Interestingly, acrosomal membrane integrity was also highest in the groups with Hep+ fraction in concentrations of 125 µg/mL. Our results showed that the addition of protein fractions did not significantly affect the plasma membrane integrity and capacitation status of stallion spermatozoa. Moreover, our results confirmed that the effect of SP proteins on the sperm functionality is concentration-dependent, as has been reported for other species. Our study significantly contributes to the lack of studies dealing with possible use of specific stallion SP fractions in the complex puzzle of the improvement of cryopreservation protocols. It is clear that improvement in this field still needs more outputs from future studies, which should be focused on the effect of individual SP proteins on other sperm functional parameters with further implication on the success of artificial insemination in in vivo conditions.

Boar seminal plasma: current insights on its potential role for assisted reproductive technologies in swine

Seminal plasma (SP) supports not only sperm function but also the ability of spermatozoa to withstand biotechnological procedures as artificial insemination, freezing or sex sorting. Moreover, evidence has been provided that SP contains identifiable molecules which can act as fertility biomarkers, and even improve the output of assisted reproductive technologies by acting as modulators of endometrial and embryonic changes of gene expression, thus affecting embryo development and fertility beyond the sperm horizon. In this overview, we discuss current knowledge of the composition of SP, mainly proteins and cytokines, and their influence on semen basic procedures, such as liquid storage or cryopreservation. The role of SP as modulator of endometrial and embryonic molecular changes that lead to successful pregnancy will also be discussed.

The Presence of Seminal Plasma during Liquid Storage of Pig Spermatozoa at 17 °C Modulates Their Ability to Elicit In Vitro Capacitation and Trigger Acrosomal Exocytosis

Although seminal plasma is essential to maintain sperm integrity and function, it is diluted/removed prior to liquid storage and cryopreservation in most mammalian species. This study sought to evaluate, using the pig as a model, whether storing semen in the presence of seminal plasma affects the sperm ability to elicit in vitro capacitation and acrosomal exocytosis. Upon collection, seminal plasma was separated from sperm samples, which were diluted in a commercial extender, added with seminal plasma (15% or 30%), and stored at 17 °C for 48 or 72 h. Sperm cells were subsequently exposed to capacitating medium for 4 h, and then added with progesterone to induce acrosomal exocytosis. Sperm motility, acrosome integrity, membrane lipid disorder, intracellular Ca²⁺ levels, mitochondrial activity, and tyrosine phosphorylation levels of glycogen synthase kinase-3 (GSK3)α/β were determined after 0, 2, and 4 h of incubation, and after 5, 30, and 60 min of progesterone addition. Results showed that storing sperm at 17 °C with 15% or 30% seminal plasma led to reduced percentages of viable spermatozoa exhibiting an exocytosed acrosome, mitochondrial membrane potential, intracellular Ca²⁺ levels stained by Fluo3, and tyrosine phosphorylation levels of GSK3α/β after in vitro capacitation and progesterone-induced acrosomal exocytosis. Therefore, the direct contact between spermatozoa and seminal plasma during liquid storage at 17 °C modulated their ability to elicit in vitro capacitation and undergo acrosomal exocytosis, via signal transduction pathways involving Ca²⁺ and Tyr phosphorylation of GSK3α/β. Further research is required to address whether such a modulating effect has any impact upon sperm fertilizing ability.

Period of Boar Ejaculate Collection Contributes to the Yearly Intra-Male Variability of Seminal Plasma Cytokines

The concentrations of cytokines in seminal plasma (SP) fluctuate over time in healthy males, weakening their practical usefulness as diagnostic tools. This study evaluated the relevance of intra-male variability in SP cytokines and to what extent the period of the year when ejaculate is collected contributes to such variability. Thirteen cytokines (GM-CSF, IFNγ, IL-1α, IL-1β, IL-1ra, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, and TNFα) were measured using the Luminex xMAP^® technology for 180 SP samples of ejaculate collected over a year from nine healthy and fertile boars. The SP samples were grouped into two annual periods according to decreasing or increasing daylight and ambient temperature. Intra-male variability was higher than inter-male variability for all cytokines. All SP cytokines showed concentration differences between the two periods of the year, showing the highest concentration during the increasing daylength/temperature period, irrespective of the male. Similarly, some cytokines showed differences between daylength/temperature periods when focusing on their total amount in the ejaculate. No strong relationship (explaining more than 50% of the total variance) was found between annual fluctuations in SP-cytokine levels and semen parameters. In conclusion, the period of the year during which ejaculates were collected helps explain the intra-male variability of SP-cytokine levels in breeding boars.

The role of seminal plasma in the liquid storage of spermatozoa

Ongoing progress in proteomic characterization of seminal plasma has stimulated research on the identification of biomarkers for male fertility and sperm preservability. So far, many studies have evaluated the benefits of reconstituting cryopreserved or sex-sorted semen with seminal plasma. Less information is available about the effect of remaining or added seminal plasma in liquid preserved semen. The interaction between seminal plasma and spermatozoa is species -specific, and within species often complex and ambiguous. This article aims to review the action of seminal plasma on sperm function in preserved semen with a focus on liquid storage. Effects of seminal plasma on sperm traits during in vitro storage are summarized for males from four domestic farm animals, namely the bull, ram, boar and stallion. Special emphasis is placed on the effect of seminal plasma on long-term stored boar semen, including novel data demonstrating the attenuating effect of protective extender on the adverse effect of seminal plasma in some boars.

Differences between first and second ejaculations regarding seminal plasma calcium, magnesium and total antioxidant capacity in dual-purpose Fleckvieh bulls and their relationships with semen quality

Artificial insemination is a well-established and widely used method for genetic improvement in cattle breeding industry. Recently, researchers have shown an increased interest in the cryoprotective effects of minerals and antioxidants on semen. Previous studies on calcium (Ca) and magnesium (Mg), two main macro-minerals, have mainly investigated their roles in mammalian spermatogenesis and fertility. In addition, the experimental data examining the semen content regarding these minerals and antioxidants from different animal species are rather controversial and there is no general agreement about their associations with semen quality. Therefore, this study was conducted to assess the seminal plasma concentrations of Ca, Mg and total antioxidant capacity (TAC) in first and second ejaculations of dual-purpose Fleckvieh bulls and to link them to the sperm characteristics of fresh and frozen-thawed semen. Sperm progressive motility after thawing was used to classify the data into three groups: < 40.00%, 40.00 to 50.00% and > 50.00%. The measurements of two minerals and TAC were carried out using spectrophotometry and enzyme-linked immunosorbent assays, respectively. The results showed that there were significant differences in several parameters of semen quality between first and second ejaculations. No significant differences were also found on Ca and Mg concentrations and Ca/Mg ratio. The TAC level was significantly higher in the first ejaculation than the second one. The findings of this study suggest that TAC is a potential marker for bull semen quality assessment in the frozen semen production industry.

The content of immunomodulatory glycoepitopes in seminal plasma glycoproteins of fertile and infertile men

According to a concept of fetoembryonic defence, protein-carbohydrate interaction may be involved in the regulation of maternal immunity that prevents rejection of allograft spermatozoa, embryo and fetus. In the present study we focussed on the evaluation of the expression of glycoepitopes that may be of crucial importance in this process: LewisY (LeY) and LewisX (LeX) as well as terminal sialylation. Polyacrylamide gel electrophoresis with sodium dodecyl sulphate was used to separate seminal plasma samples of fertile (n=10) and infertile (n=103) men; these were then probed with lectins specific to fucose (Lotus tetragonolobus agglutinin and Ulex europaeus agglutinin) and sialic acid (Sambucus nigra agglutinin and Maackia amurensis agglutinin). Differential expression of α2,3-bound sialic acid was found in six out of seven analysed bands, whereas differences in the other analysed glycoepitopes were found in fewer numbers of bands. Mass spectrometry analysis focussed on the identification of proteins carrying glycans with immunomodulatory epitopes, including fibronectin, lactoferrin, clusterin, zinc-α2-glycoprotein, prostate acid phosphatase and prostate-specific antigen; these should be submitted to further detailed analysis.

Extenders modify the seminal plasma ability to minimize freeze-thaw damage on ram sperm

Seminal plasma (SP) proteins interact with sperm plasma membrane (PM) modulating its functionality. It has been shown that SP proteins can reverse the damage caused by freeze-thaw; however in these studies, SP has been added to washed sperm (i.e., cells depleted from homologous SP and extender). The aim of the current study was to assess whether the egg yolk-based extender (EY) modifies SP ability to ameliorate sperm parameters in frozen-thawed ram spermatozoa. Ejaculates were diluted in EY or soybean lecithin-based extender (SL) and evaluated before and after freezing to measure the cell damage according to the extender. Even when all classical parameters decreased after freezing, as expected (p < .05), there was no effect of the extender. SP treatment was applied after freeze-thaw. Sperm were incubated with SP (20% v/v) in the presence of either EY or SL, and sperm parameters were assessed after thawing compared with the same treatments after Percoll sperm selection (washed). Treatments with 20% SP improved sperm total and progressive motility compared with controls regardless of washing and extender (p < .05); however, washed sperm showed higher percentage of total sperm motility compared with those unwashed (p < .05). Moreover, treatment with 20% SP showed significantly higher percentages of PM integrity, sperm with intact acrosomes, integrity of chromatin and non-capacitated sperm in samples diluted with EY when washed before treatment compared with the other conditions (p < .05). It was concluded that the presence of the extenders and particularly egg yolk alters the SP capacity to reduce the cryodamage.

Relative content of Niemann-Pick C2 protein (NPC2) in seminal plasma, but not that of spermadhesin AQN-1, is related to boar sperm cryotolerance

Variation between and within boar ejaculates in terms of their ability to withstand freeze-thawing is a limitation for sperm cryopreservation. Consequently, searching for freezability markers not only in sperm but also in seminal plasma (SP) is imperative. The present study aimed to evaluate the relationship between cholesterol content, relative levels of NPC2 and AQN-1 at two different holding times (0 h: HT0 and 24 h: HT24) at 17 °C, and boar sperm freezability. Forty-five ejaculates were cryopreserved and subsequently classified as of good (GFE) or poor (PFE) freezability according to their post-thaw sperm viability and total motility. Prior to cryopreservation, relative abundances of two SP proteins (NPC2 and AQN-1) and cholesterol content in sperm and SP were determined through immunoblotting and colorimetric methods, respectively. These determinations were made after ejaculation (HT0) and after 24 h of storage at 17 °C (HT24). Two bands for NPC2 protein (16 kDa and 19 kDa) were identified. Relative amounts of the 16 kDa-band were significantly (P < 0.05) higher in poor (PFE) than in good (GFE) freezability ejaculates both at HT0 and HT24, whereas those of the 19 kDa-band were significantly (P < 0.05) higher in PFE than in GFE at HT24 only. In the case of AQN-1, no significant differences between GFE and PFE were observed. In addition, no variations in the cholesterol content of sperm and SP were observed either between HT0 and HT24 or between GFE and PFE. We can conclude that the content of two NPC2 isoforms in SP, but not of that of spermadhesin AQN-1, may be involved in the sperm resilience to withstand freeze-thawing procedures and may predict ejaculate freezability. While a possible mechanism through which NPC2 during HT could affect boar sperm cryotolerance is suggested to be related to its ability to bind the plasma membrane cholesterol, further research is warranted.

Epididymal and ejaculated sperm differ on their response to the cryopreservation and capacitation processes in mouflon (Ovis musimon)

Spermatozoa must undergo the process of capacitation to fertilize the egg which involves a cell destabilizing process. Capacitation-like changes such as protein tyrosine phosphorylation (PTP) are associated with cryopreservation. The aim of this study was to compare the cryoresistance and capacitation response of epididymal and ejaculated sperm of European mouflon (Ovis musimon). Post-thaw sperm parameters were analysed from epididymal and ejaculated samples cryopreserved by slow-freezing or ultrarapid-freezing for comparison. Sperm capacitation status was assessed by the semiquantification of PTP levels, cell localization of PTP and kinematic clustering. Epididymal sperm had higher cryoresistance than ejaculated sperm in both freezing techniques, and slow-freezing rendered better results than ultrarapid-freezing in both sperm samples. Ejaculated sperm had higher PTP levels than epididymal sperm and, additionally, ejaculated sperm showed higher phosphorylation in capacitating (CA) than in non-capacitating (NCA) conditions while there was no effect of medium in epididymal sperm. There was a higher tail PTP in CA than in NCA conditions in both types of sperm. Kinematic analysis revealed that the cluster associated with hyperactivated movement increased in ejaculated sperm incubated in CA whereas no effect of medium was observed in epididymal sperm clusters. In conclusion, epididymal sperm showed better freezability and lower capacitation status compared to ejaculated sperm.

Cryopreservation and egg yolk extender components modify the interaction between seminal plasma proteins and the sperm surface

It is known that the addition of seminal plasma (SP) or SP proteins either before freezing or post thawing show contradictory results on sperm quality and fertility due to the interference between SP and the extender. Thus, the aim of this study was to determine whether egg yolk (EY) interferes with SP ability to protect the functionality and fertility of ram sperm during freeze-thawing by modifying the interaction between seminal plasma proteins and the sperm plasma membrane. Ejaculated or epididymal ram sperm collected during the breeding season were incubated with SP in the presence or absence of EY or soybean lecithin-based extenders before cryopreservation. No significant differences were observed after thawing in sperm quality (total and progressive sperm motility, membrane integrity, plasma membrane functionality, percentage of non-capacitated sperm) between the extenders, either in presence or absence of seminal plasma (P ≥ 0.05). The amount of proteins retained by the sperm surface normalized to number of cells was diminished after freeze-thawing compared to their fresh counterparts for all the treatments (P < 0.05), demonstrating that cryopreservation weakens the interaction between external proteins and the sperm surface. The electrophoretic analysis of sperm-bound proteins showed that the retention of several SP peptides onto the sperm surface (based on densitometry estimation) was affected by the presence of the diluents on both ejaculated and epididymal sperm (P < 0.05). Moreover, variation was observed in the protein pattern after thawing compared to the corresponding fresh samples, suggesting that freezing affects surface protein profile. Pregnancy rate after artificial insemination at fixed time was higher (P < 0.05) for samples treated with reconstituted with heterologous SP compared to those supplemented with 20% additional seminal plasma or control samples despite the presence of EY. In conclusion, both freeze-thawing and EY components affected the interaction among seminal plasma proteins and the sperm surface, although these changes were not reflected on different sperm quality parameters under our experimental conditions. In vivo fertility of sperm reconstituted with exogenous SP before freezing was improved even in the presence of EY components considering an optimal ratio SP:sperm.

The Potential Role of Seminal Plasma in the Fertilization Outcomes

For human infertility both male and female factors may be equally important. Searching for molecular biomarkers of male infertility, neglected for decades, and the attempts to explain regulatory mechanisms of fertilization become thus extremely important. Apart from examination of the structure and function of male gametes, also the possible importance of seminal plasma components should be considered. In this article we discuss data that indicate for the substantial significance of active seminal plasma components for conception and achievement of healthy pregnancy. Seminal plasma impact on the storage and cryopreservation of human and animal sperm and regulatory role of glycodelin on human sperm capacitation as well as hypothesized course of female immune response to allogenic sperm and conceptus has been discussed. The possible involvement of carbohydrates in molecular mechanism of fetoembryonic defense has been also mentioned.

Binder of Sperm Proteins 1 and 5 have contrasting effects on the capacitation of ram spermatozoa

Binder of Sperm Proteins (BSPs) are the most abundant seminal plasma protein family in the ram and bull. They have been extensively studied in the bull but less is known about their function in ovine seminal plasma and current knowledge suggests that BSPs may have different effects in these two species. In the bull, they facilitate capacitation and destabilize the sperm membrane during in vitro handling, whereas in the ram, they appear to stabilize the sperm membrane and prevent cryopreservation-induced capacitation-like changes. Further investigation into the effects of BSPs on ram spermatozoa under capacitating conditions is required to further clarify their physiological roles in the ram. We investigated the effects of Binder of Sperm Proteins 1 and 5 on epididymal ram spermatozoa in conditions of low, moderate, and high cAMP. BSPs had minimal effects on sperm function in low-cAMP conditions, but caused significant changes under cAMP upregulation. BSP1 stabilized the membrane and qualitatively reduced protein tyrosine phosphorylation, but significantly increased cholesterol efflux and induced spontaneous acrosome reactions. BSP5 slightly increased spontaneous acrosome reactions and caused sperm necrosis. However, BSP5 had minimal effects on membrane lipid order and cholesterol efflux and did not inhibit protein tyrosine phosphorylation. These findings demonstrate that under maximal cAMP upregulation, BSP1 affected ram spermatozoa in a manner comparable to bull spermatozoa, while BSP5 did not.

Inhibition of influenza virus activity by the bovine seminal plasma protein PDC-109

A number of viruses causing sexually transmissible diseases are transmitted via mammalian seminal plasma. Several components of seminal plasma have been shown to influence those viruses and their physiological impact. To unravel whether components of seminal plasma could affect viruses transmitted via other pathways, it was investigated here whether the bovine seminal plasma protein PDC-109, belonging to the Fn-type 2 protein family, influences the activity of influenza A viruses, used as a model for enveloped viruses. We found that PDC-109 inhibits the fusion of influenza virus with human erythrocyte membranes and leads to a decreased viral infection in MDCK cells. In the presence of the head group of the phospholipid phosphatidylcholine, phosphorylcholine, the inhibitory effect of PDC-109 was attenuated. This indicates that the impact of the protein is mainly caused by its binding to viral and to erythrocyte membranes thereby interfering with virus-cell binding. Our study underlines that Fn-type 2 proteins have to be considered as new antiviral components present in mammalian seminal plasma.

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.

Potential of seminal plasma to improve the fertility of frozen-thawed boar spermatozoa

Artificial insemination (AI) is widely used for livestock breeding. Although sperm cryopreservation is the most efficient method for long-term storage, its use for porcine AI is marginal, because of its dramatic impact on sperm quality. While the removal of seminal plasma is a routine practice prior to porcine sperm cryopreservation, its beneficial role on sperm function has not been investigated in as much detail. In this context and despite seminal plasma being regarded as a mere vehicle of sperm, mounting evidence indicates that it could be positive for porcine sperm fertility. In effect, not only is seminal plasma able to interact with the female reproductive tract after mounting/insemination, but it has been demonstrated it modulates sperm function. For this reason, the composition of this fluid and its proteome have begun to be investigated in order to elucidate whether its components play any role in sperm function, fertility and cryotolerance. Previous research has demonstrated that seminal plasma may maintain the quality and fertilizing ability of frozen-thawed boar spermatozoa when added before or after cryopreservation. However, a large variety of results have been reported with both beneficial and detrimental effects, including studies in which no influence has been observed. This review examines the composition of porcine seminal plasma and summarizes the available published studies regarding seminal plasma supplementation to spermatozoa before or after freeze-thawing. The take-home message of this article is that clearing up the role of seminal plasma in sperm cryotolerance may increase the reproductive performance of frozen-thawed boar spermatozoa.

Evaluation of the cryoprotective effect of seminal plasma on llama (Lama glama) spermatozoa

In South American camelids, sperm survival is low after thawing and poor results are obtained when artificial insemination is performed with cryopreserved semen. The aim of this study was to evaluate the effect of different percentages (10% and 50%) of seminal plasma added prior to the process of cryopreservation and also to evaluate the absence of seminal plasma on llama sperm survival after freezing and thawing. A total of 15 ejaculates from five adult llama males (n = 5; r = 3) were evaluated. A significant decrease in sperm motility, viability, membrane function and intact acrosomes was observed in thawed samples (0%, 10% and 50%) when compared to raw semen. Neither morphology nor chromatin condensation was altered in all thawed samples (p > 0.05), but a significant increase (p < 0.05) in the percentage of spermatozoa with fragmented DNA was observed after thawing all samples compared to raw semen. Higher percentages of total and progressive sperm motility were observed when 0% and 10% of seminal plasma were used compared to 50%. However, no statistical differences were established for sperm viability, membrane function, morphology, acrosome status and DNA quality between thawed treatments. To conclude, neither of the percentages of seminal plasma used showed superiority nor cryoprotective effect on llama sperm survival.

In vitro aging of boar spermatozoa: role of sperm proximity and seminal plasma

BACKGROUND

Knowledge on the effect of seminal plasma on sperm function in extended semen during in vitro storage is lacking.

OBJECTIVES

The aim was to examine the interactive role of sperm concentration and seminal plasma concentration on boar sperm function during in vitro aging.

MATERIAL AND METHODS

Experiment 1: Twenty-one boar ejaculates were aliquoted with Beltsville Thawing Solution into five semen doses containing between 32.5 and 8.5 × 10⁶  sperm/mL. Experiment 2: Semen samples (n = 8) containing 18 × 10⁶ or 10 × 10⁶  sperm/mL with their natural amount of seminal plasma and 10 × 10⁶  sperm/mL substituted with autologous seminal plasma to the same concentration as in doses with 18 × 10⁶  sperm/mL were prepared. Experiment 3: Four variants of semen doses containing 18 × 10⁶ or 10 × 10⁶  sperm/mL with either 10% or 0.5% (v/v) seminal plasma were used. Lipid peroxidation was assessed using Bodipy 581/591 in samples (n = 8) with two different sperm concentrations. Semen was examined during 144-h storage at 17 °C by computer-assisted semen analysis and flow cytometry.

RESULTS

Experiment 1: 3D kinematic patterns revealed a concentration- and time-dependent loss of sperm kinematics in samples with < 23 × 10⁶  sperm/mL (p < 0.05). Percent viable spermatozoa with high mitochondria membrane potential were lower (p < 0.05) in samples with < 15 × 10⁶  sperm/mL. Experiment 2: Seminal plasma supplementation in samples with 10 × 10⁶  sperm/mL did not restore the loss of sperm kinematics (p > 0.05). Experiment 3: At 144 h, motility was lowest in samples containing 10 × 10⁶  sperm/mL and 10% (v/v) seminal plasma (p < 0.05). Sperm lipid peroxidation did not differ between samples with different sperm concentration.

CONCLUSION

Long-term exposure to seminal plasma has a negative impact on in vitro-aged boar spermatozoa. Reduced sperm-to-sperm proximity but not the reduction of seminal plasma limits sperm function in long-term stored boar semen.

Recent advances in bovine sperm cryopreservation techniques with a focus on sperm post-thaw quality optimization

Sperm cryopreservation facilitates the storage and transport of germplasm for its use in artificial insemination (AI) and other advanced reproductive technologies. The cryopreservation process can damage sperm and compromise functionality. Several cryobiological studies have found that the physical and biological factors that affect sperm survival at low temperatures during the cryopreservation process often involve the integrity of sperm membrane. In this review, the behaviour of the sperm membrane against cooling, cold shock, ice crystal formation, oxidative stress, osmotic changes, reorganization of the lipid bilayer and addition of cryoprotective agents (CPA) is discussed. In addition, the phenomenon of reactive oxygen species (ROS) and its relationship with the cryopreservation process is also described. Semen cryopreservation techniques have progressed slowly in past years, and the current performance, measured as post-thawed survival, is not very different compared to past decades. Recent advances in understanding the structure of the cell membrane, its function and metabolism have driven to new conservation systems, including lyophilization and vitrification. However, none of these technologies is commercially available, although its future appears very promising.

Seminal plasma amino acid profile in different breeds of chicken: Role of seminal plasma on sperm cryoresistance

Seminal plasma is a key biological fluid that modulates sperm function in the reproduction process. However, its role in sperm biotechnologies is scarce in poultry. The aims of the present study were to study the amino acids profile and total proteins of seminal plasma in 12 Spanish chicken breeds and to investigate the role of seminal plasma on cryoresistance of rooster sperm. To investigate the role of seminal plasma on cryoresistance, diluted pooled semen samples were cryopreserved in the presence and absence of seminal plasma. Glutamic acid was the most abundant free amino acid in seminal plasma, followed by alanine, serine, valine, and glycine. There was an influence of breed (P<0.05) on the percentage of viable sperm after freezing-thawing of samples with seminal plasma. Cluster analysis revealed that White Prat, Black Castellana, Blue Andaluza, Quail Castellana, and Red-Barred Vasca returned the best freezing-thawing response (good freezers). There was a positive correlation between seminal plasma concentrations of valine, isoleucine lysine, leucine and post thaw viability. The evaluation of fertilization capacity of frozen-thawed semen from the breeds White Prat ('good freezer') and Black-Red Andaluza ('bad freezer') showed that good freezer had higher fertility (20/68, 29.4%) compared to bad freezer breed (14/76, 18.4%), even if the difference was not significant (P = 0.08). The TUNEL assay revealed that freezing/thawing procedures in presence of seminal plasma provoked higher DNA fragmentation in most of the breeds, with a positive correlation between seminal alanine, valine, isoleucine, methionine, leucine, tyrosine, phenylalanine concentrations and DNA integrity. DNA fragmentation was lower in absence of seminal plasma and the breed effect on sperm viability was highly reduced. It is concluded that specific seminal plasma amino acids were associated with post-thaw percentage of viable sperm and DNA integrity. The removal of seminal plasma decreases the variability of the results and DNA fragmentation damages.

The Proteome of Pig Spermatozoa Is Remodeled During Ejaculation

Proteins are essential for sperm function, including their fertilizing capacity. Pig spermatozoa, emitted in well-defined ejaculate fractions, vary in their functionality, which could be related to different sperm protein composition. This study aimed (i) to update the porcine sperm proteome and (ii) to identify proteins differentially expressed in mature spermatozoa from cauda epididymis and those delivered in separate ejaculate fractions. Ejaculates from nine mature and fertile boars were manually collected in three separate portions: the first 10 ml of the sperm-rich ejaculate fraction (SRF), the rest of the SRF and the post-SRF. The contents of cauda epididymides of the boars were collected post-mortem by retrograde duct perfusion, generating four different semen sources for each boar. Following centrifugation, the resulting pellets of each semen source were initially pooled and later split to generate two technical replicates per source. The resulting eight sperm samples (two per semen source) were subjected to iTRAQ-based 2D-LC-MS/MS for protein identification and quantification. A total of 1,723 proteins were identified (974 of Sus scrofa taxonomy) and 1,602 of them were also quantified (960 of Sus scrofa taxonomy). After an ANOVA test, 32 Sus scrofa proteins showed quantitative differences (p < 0.01) among semen sources, which was particularly relevant for sperm functionality in the post-SRF. The present study showed that the proteome of boar spermatozoa is remodeled during ejaculation involving proteins clearly implicated in sperm function. The findings provide valuable groundwork for further studies focused on identifying protein biomarkers of sperm fertility.

Protein and lipid species in seminal plasma of fertile Holstein-Friesian bulls

Protein and lipid molecules in seminal plasma (SP) collected from fertile bulls were investigated. Semen was collected from 10 bulls (2 ejaculates each) and examined for standard semen analysis. Raw SP was recovered by centrifugation and total protein (TP) concentration was determined using a refractometer. Raw SP was desalted using a Sephadex G-25 desalting column then both raw and desalted SP was subjected to SDS-PAGE. Neutral lipids and phospholipids of raw and desalted SP were separated by thin-layer chromatography (TLC). The results revealed that, all bulls had normal semen characteristics and TP concentration in SP ranged from 7.0 to 10.4 g/dL except bull No. 6 had a relatively low concentration of 4.9 to 6.8 g/dL. Neither proteins nor lipids species were different between raw and desalted SP. Seventeen proteins were detected ranging from 8.5 to 185.8 kDa, and those of 12, 13.5, 15, 21, 23 and 38 kDa were predominant. Notably, proteins of 10, 17.5, 19, 21, 80 and 185.8 kDa might be new candidates of SP proteins (SPPs). The detected neutral lipid spots corresponded to cholesterol, 1,2-dimyristoyl glycerol, 1,2-dioleoyloglycerol, 1,3-dimyristoyl glycerol and 1,3-dioleoyloglycerol. The detected phospholipids spots corresponded to non-migrating phospholipids, sphingomyelin (SM), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylethanolamine (PE), cerebroside and polyglycerol phosphatide. Cholesterol represents the major molecule of neutral lipids, whereas SM, PC, PI and PE represent the major phospholipids. Noteworthy, there were 2 species of diacylglycerol (DAG) and 3 species of PI in bovine SP. In conclusion, this study gave a general picture of SP protein and lipid species in fertile bull semen, which might serve as fundamental knowledge for either semen analysis or prediction of male fertility.

Transgenerational Impact of Environmental Change

The ability to adapt to changing environmental conditions is critical for any species to survive. Many environmental changes occur too rapidly for an organism's genome to adapt in time. Accordingly, being able to modify either its own phenotype, or the phenotype of its offspring to better suit future anticipated environmental conditions could afford an organism a significant advantage. However, a range of animal models and human epidemiological data sets are now showing that environmental factors such as changes in the quality or quantity of an individual's diet, temperature, stress or exposure to pollutants can all adversely affect the quality of parental gametes, the development of the preimplantation embryo and the health and wellbeing of offspring over multiple generations. This chapter will examine transgenerational effects of both maternal and paternal environmental factors on offspring development and wellbeing in both human and animal model studies. Changes in the epigenetic status of either parental or grand-parental gametes provide one candidate mechanism through which the impacts of environmental experience can be passed from one generation to another. This chapter will therefore also focus on the impact of parental and grand-parental diet on epigenetic transgenerational inheritance and offspring phenotype.

Postthaw Addition of Autologous Seminal Plasma Improves Sperm Motion Characteristics in Fair and Poor Freezer Stallions

During semen processing for cryopreservation, most seminal plasma is usually removed, and components with protective effects on sperm may be missing after thawing and within the female reproductive tract. The present study evaluated the effect of postthaw addition of autologous seminal plasma on motion characteristics of stallion sperm with fair (n = 4) or poor (n = 3) freezability. Therefore, pure seminal plasma (group SP1), seminal plasma combined with fresh semen extender (group SP2), or seminal plasma mixed with freezing extender (group SP3) were used to fill 0.5 mL straws and frozen similar to stallion semen. Postthawing, semen samples (n = 42) were diluted either with semen extender (group FT) or with seminal plasma (n = 126) of groups SP1 to SP3 to 25 × 10⁶ sperm/mL. In fair freezer stallions, total and progressive motilities were higher in group FT than in group SP1 (P < .05), but there was no difference in poor freezing stallions among groups (P > .05). However, comparing individual stallions, positive effects of seminal plasma on total or progressive motility were detected in two stallions. Curvilinear velocity increased in groups SP2 and SP3 in fair freezer stallions and in all groups with seminal plasma compared with group FT in poor freezer stallions (P < .05). Although straightness was higher in groups SP2 and SP3 compared with group FT in fair freezer stallions (P < .05), there was no difference among groups in stallions with poor freezability (P > .05). Average lateral head displacement did not change among groups of fair freezer stallions (P > .05) but was higher in groups SP2 and SP3 than in group FT in poor freezer stallions (P < .05). Beat cross frequency was higher in all groups diluted with seminal plasma postthawing in fair freezer stallions (P < .05), but only in group SP1 than in group FT in poor freezer stallions (P < .05). The addition of autologous seminal plasma to frozen-thawed semen can improve motion characteristics of stallions with fair and poor freezability. This is a valuable additional protocol for laboratories dealing with cryopreservation of stallion semen and for veterinarians working with fair or poor freezer stallions.

Patterns of expression of sperm and seminal plasma microRNAs in boar semen

Although sperm and seminal plasma differ in their origin, biophysical and biochemical properties of seminal plasma influence the sperm function. Seminal plasma is a fluid medium containing substances from testes, epididymides and accessory glands. Composition of seminal plasma varies among animal species and in boars, prostate and bulbourethral glands are major contributors to the volume and contents. While the origin of some components of seminal plasma are known, the source of recently discovered seminal plasma microRNAs remains unknown, in part due to the difficulty of recovering and characterizing RNA from porcine sperm and seminal plasma. To test the hypothesis that seminal plasma miRNAs interact with sperm, the first objective was to validate protocols for recovering RNAs from porcine seminal plasma and sperm, whereas the second objective was to characterize expression patterns of 84 prioritized microRNAs employing real time PCR methodology. The study identified a relationship between sperm and seminal plasma microRNAs, based on the normalized threshold cycle of amplifying cDNA in sperm and seminal plasma from the same semen of Landrace boars. Therefore, it was concluded that seminal plasma miRNAs may originate from sperm or these miRNAs may shuttle between sperm and seminal plasma in order to facilitate cell-to-cell communication.

Absence of seminal plasma from sperm-rich fraction decreases boar sperm quality characteristics during the course of liquid storage

Seminal plasma (SP), the fluid that surrounds the sperm cells, is known to exert substantial influence on sperm physiology. The SP has a pivotal role in sperm function in vivo, and due to its components, it functions in an ambiguous manner in vitro, simultaneously possessing deleterious and beneficial effects. This experiment aimed to describe the differences between the presence or absence of SP from the sperm-rich fraction on some spermatozoa characteristics (kinetics, plasma and acrosome membrane integrity, lipid peroxidation and capacitation-like changes). Furthermore, this experiment focused on distinguishing the effects of SP on the variables evaluated from the effects of centrifugation during SP removal. Total and progressive sperm motility, as well as integrity of plasma and acrosome membranes, were less (P <  0.05) in the absence of SP. Membrane lipid peroxidation (P <  0.05) and sperm membrane stability (P < 0.05) did not differ among treatments. The SP from the sperm-rich fraction is important for the maintenance of adequate structural and functional characteristics of extended liquid boar semen and should be present in seminal doses throughout storage. Furthermore, the detrimental effect on the variables evaluated was caused solely by the absence of SP and not by the process of removal through centrifugation at 500 x g for 10 min.

Does advanced age affect reproductive variables, semen composition, and liquid semen storage during different seasons in Boujaâd rams?

The present research was conducted to evaluate the effects of season and age on scrotal circumference (SC), semen characteristics, semen composition, and sperm motility during liquid storage in Boujaâd rams. Semen was collected throughout 1 year from April 2014 to March 2015. Two ram groups, namely older rams including animals aged 5.5 to 6 years of age, and younger rams including animals aged 2.5 to 3 years of age were used. Scrotal circumferences, semen characteristics, and some biochemical variables from semen were measured. After collection and evaluation, the semen was extended in skim milk (SM) at 15 °C to a concentration of 0.8 × 10⁹ spermatozoa/ml. Thereafter, samples were evaluated at different storage times (0, 8, and 24 h). The results indicate that older rams had greater values of SC, lesser semen quality, protein, lipid, and cholesterol concentrations than younger rams. Nevertheless, for both groups there were the least values for semen quality and semen composition in winter. The semen collected from younger rams had greater motility after liquid storage compared with that of the older rams. The least semen quality after liquid storage was recorded in the winter compared with the other seasons of the year for both age groups. In conclusion, results of the present study indicate that older Boujaâd sheep have lesser semen quality, different semen composition than younger rams after liquid storage and during different seasons of the year. Furthermore, there was a strong correlation between semen composition and motility of stored ram semen.

Presence of Fertility-associated antigen on sperm membrane corresponds to greater freezability potential of Frieswal bull semen

Several studies have shown relationship of semen freezability with Fertility-associated antigen (FAA) in purebreds. Objectives of present investigation were to determine presence of FAA in Frieswal bull semen and its relationship with freezability. Study involved separation of seminal plasma (SP, FAA – or +) and sperm membranes (SM, FAA – or +), electrophoresis, protein content and quality assessment (n=36).Five groups were: Group-I (19.4%, SP+ve/SM+ve); Group-II (22.2%, SP-ve/SM+ve); Group-III (25%, SP+ve/SM-ve); Group-IV (16.7%, SP-ve/SM-ve), and Group-V (16.7%, unprocessed, initial progressive motility ≤30%, negative control).At postthaw stage, Group-I and -II showed significantly higher (p< 0.001) freezabilitythan FAA-SM-ve groups. Moreover, Group-III with FAA in seminal plasma but not on membrane showed better post-thaw motility than Group-IV, which totally lacked FAA. Our results have shown that 28–30 kDa protein is present in SP and SM of majority of Frieswal bulls and presence of FAA in SM confers appreciable improvement in freezability.