Increased male fertility using fertility-related biomarkers

Evaluation of sperm quality and male fertility: The use of molecular markers in boar sperm and seminal plasma

In pig production, the optimization of artificial insemination (AI) efficiency significantly relies on the accurate assessment of semen quality and fertility of boars. Traditional methods such as conventional seminogram techniques, although long-standing, exhibit limited sensitivity in predicting boar fertility, warranting the exploration of novel molecular markers. This review synthesizes the current knowledge on the utilization of molecular markers for semen quality evaluation and male fertility prediction in boars, providing an in-depth examination of molecular markers in this context. Specifically, the present work delves into the potential of OMICs technologies, encompassing genetic and genomic approaches, transcriptomics, proteomics, and metabolomics. A diverse array of molecular markers, including genomic regions associated with sperm quality and male fertility, chromatin integrity, mitochondrial DNA content, mRNA and non-coding RNA signatures, as well as proteins and metabolites in sperm and seminal plasma, are identified as promising molecular markers for fertility prediction in boars. Furthermore, the need of validating biomarkers and their practical implementation in AI centres is here emphasized. Addressing these considerations and integrating molecular markers within the swine breeding field holds the potential to enhance reproductive management practices and optimize productivity in boar breeding programs. This integration can significantly improve overall efficiency within the pig breeding industry.

3-chloro-1,2-propanediol induces oxidative stress and promotes testicular damage and infertility in rats through CYP2C9

3-chloro-1,2-propanediol (3-MCPD) is a newly discovered food process pollutant with nephrotoxicity. And the mechanism by which 3-MCPD affects male spermatogenesis has not been fully studied. Cell viability, blood-testis barrier (BTB) related protein, progesterone content, reactive oxygen species (ROS) generation, and cell apoptosis were determined by a CCK8 assay, western blot, ELISA, flow cytometry, and TUNEL staining, respectively. Wistar rats were divided into three groups: low-dose 3-MCPD, high-dose 3-MCPD, and control. Sperm parameters, hormonal levels, and biomarkers of oxidative stress in the testis and epididymis were detected by ELISA. Multiple molecular experiments including molecular docking and western blot were used to elucidate the underlying mechanisms. 3-MCPD affects testicular cell activity, and promotes ROS production and apoptosis. Disrupting the integrity of BTB in the body, downregulating sex hormones and sperm quality, and promoting apoptosis. 3-MCPD may function through CYP2C9. This study preliminarily explores the mechanism by which 3-MCPD affects spermatogenesis. It was found that 3-MCPD destroys the structure and function of BTB and damages the testicular function of male mice, thus affecting the process of spermatogenesis via CYP2C9.

Bottom-up approach to deciphering the targets of the ubiquitin-proteasome system in porcine sperm capacitation

Capacitation is an essential post-testicular maturation event endowing spermatozoa with fertilizing capacity within the female reproductive tract, significant for fertility, reproductive health, and contraception. By using a human-relevant large animal model, the domestic boar, this study focuses on furthering our understanding of the involvement of the ubiquitin-proteasome system (UPS) in sperm capacitation. The UPS is a universal, evolutionarily conserved, cellular proteome-wide degradation and recycling machinery, that has been shown to play a significant role in reproduction during the past two decades. Herein, we have used a bottom-up proteomic approach to (i) monitor the capacitation-related changes in the sperm protein levels, and (ii) identify the targets of UPS regulation during sperm capacitation. Spermatozoa were capacitated under proteasomal activity-permissive and inhibiting conditions and extracted sperm proteins were subjected to high-resolution mass spectrometry. We report that 401 individual proteins differed at least two-fold in abundance (P < 0.05) after in vitro capacitation (IVC) and 13 proteins were found significantly different (P < 0.05) between capacitated spermatozoa with proteasomal inhibition compared to the vehicle control. These proteins were associated with biological processes including sperm capacitation, sperm motility, metabolism, binding to zona pellucida, and proteasome-mediated catabolism. Changes in RAB2A, CFAP161, and TTR during IVC were phenotyped by immunocytochemistry, image-based flow cytometry, and Western blotting. We conclude that (i) the sperm proteome is subjected to extensive remodeling during sperm capacitation, and (ii) the UPS has a narrow range of distinct protein substrates during capacitation. This knowledge highlights the importance of the UPS in sperm capacitation and offers opportunities to identify novel pharmacological targets to modulate sperm fertilizing ability for the benefit of human reproductive health, assisted reproductive therapy, and contraception, as well as reproductive management in food animal agriculture.

Exploring the full potential of sperm function with nanotechnology tools

Sperm quality is essential to guarantee the success of assisted reproduction. However, selecting high-quality sperm and maintaining it during (cryo)preservation for high efficiency remains challenging in livestock reproduction. A comprehensive understanding of sperm biology allows for better assessment of sperm quality, which could replace conventional sperm analyses used today to predict fertility with low accuracy. Omics approaches have revealed numerous biomarkers associated with various sperm phenotypic traits such as quality, survival during storage, freezability, and fertility. At the same time, nanotechnology is emerging as a new biotechnology with high potential for use in preparing sperm intended to improve reproduction in livestock. The unique physicochemical properties of nanoparticles make them exciting tools for targeting (e.g., sperm damage and sexing) and non-targeting bioapplications. Recent advances in sperm biology have led to the discovery of numerous biomarkers, making it possible to target specific subpopulations of spermatozoa within the ejaculate. In this review, we explore potential biomarkers associated with sperm phenotypes and highlight the benefits of combining these biomarkers with nanoparticles to further improve sperm preparation and technology.

Genome-wide detection of runs of homozygosity and heterozygosity in Tunchang pigs

Tunchang pigs, mainly distributed throughout Hainan Province of China, are well-known for their superior meat quality, crude feed tolerance, and adaptability to high temperatures and humidity. Runs of homozygosity (ROH) can provide valuable information about the inbreeding coefficient in individuals and selection signals that may reveal candidate genes associated with key functional traits. Runs of heterozygosity (ROHet) are commonly associated with balance selection, which can help us understand the adaptive evolutionary history of domestic animals. In this study, we investigated ROHs and ROHets in 88 Tunchang pigs. We also compared the estimates of inbreeding coefficients in individuals calculated based on four methods. In summary, we detected a total of 16 ROH islands in our study, and 100 genes were found within ROH regions. These genes were correlated with economically important traits such as reproduction (e.g., SERPIND1, HIRA), meat quality (e.g., PI4KA, TBX1), immunity (e.g., ESS2, RANBP1), adaption to heat stress (TXNRD2 and DGCR8), and crude food tolerance (TRPM6). Moreover, we discovered 18 ROHet islands harbouring genes associated with reproduction (e.g., ARHGEF12, BMPR2), immune system (e.g., BRD4, DNMT3B). These findings may help us design effective breeding and conservation strategies for this unique breed.

Application of sperm motion kinematics and motility-related proteins for prediction of male fertility

The selection of superior sires is paramount for enhancing the efficiency of animal production in the livestock industry. However, semen quality assessment still relies on conventional semen analysis techniques in both animals and humans. Despite extensive efforts to develop various biomarkers for more accurate and precise predictions of male fertility potential, more effective physiological indicators and advance potential biomarkers are needed. Herein, we aimed to develop new potential biomarkers related to sperm motion kinematics for male fertility prediction. We first evaluated sperm motion kinematic parameters and expression levels of sperm motility-related proteins of 30 Duroc boars. We then explored the correlation between litter size, sperm motion kinematics parameters, and sperm motility-related proteins. Progressive sperm motility (%), rapid sperm motility (%), slow sperm motility (%), straight-line velocity (μm/s), linearity (%), beat cross frequency (Hz), mean angular displacement (degree), wobble (%) were correlated with litter size. Furthermore, the expression of axonemal dynein light intermediate polypeptide 1 (DNALI1) and radial spoke head protein 9 homolog (RSPH9) correlated with litter size. The overall accuracy exceeded 60% for predicting litter size using these sperm motion parameters and proteins. Notably, our study observed an increase in litter size after predicting litter size using these parameters and proteins. Thus, sperm motion kinematic parameters and protein expression, particularly of DNALI1 and RSPH9, could serve as new biomarkers for male fertility. These results may contribute to improved understanding of the mechanisms underlying sperm motility.

Correlation between Rab3A Expression and Sperm Kinematic Characteristics

Ras-related (Rab) proteins, integral members of the monomeric G-protein family, play a pivotal role in regulating intracellular vesicular transport. These proteins contribute to male reproductive processes, specifically in acrosome formation, exocytosis, and sperm motility. Although a prior study indicated a correlation between Rab3A and sperm motility, including motion kinematic parameters such as mean dance, this association has only been explored within a limited sample size. Therefore, further verification is required to confirm the correlation between Rab3A and sperm motility parameters. In the present study, Rab3A expression, sperm motility, and motion kinematic parameters were analyzed in 150 boar spermatozoa. Additionally, correlations between Rab3A expression and sperm kinematic characteristics were evaluated statistically. The results revealed significant associations between Rab3A protein expression levels and various motion kinematic parameters. Specifically, Rab3A levels exhibited positive correlations with average path velocity (p <0.05), mean amplitude of lateral head displacement (p <0.05), and curvilinear velocity (p <0.01). Consequently, it is proposed that Rab3A protein plays a crucial role in male fertility through its correlation with sperm kinematic characteristics, making it a potential marker for sperm motility-related assessments.

Kojic acid inhibits pig sperm apoptosis and improves capacitated sperm state during liquid preservation at 17°C

The parameters of sperm apoptosis and capacitation during liquid storage at 17°C can indicate the quality of pig sperm and the potential development of early embryos. However, the effect of kojic acid (KA) on semen preservation and its mechanism has not been fully understood. In this study, we discovered that adding KA to the diluent improved the antioxidant capacity of sperm mitochondria, maintained the normal structure of sperm mitochondria, and reduced sperm apoptosis. Western blot analysis revealed that KA prevented the release of Cytochrome c from mitochondria to the cytoplasm, reduced the expression of pro-apoptosis proteins cleaved Caspase-3 and cleaved Caspase-9, and increased the expression of the antiapoptosis protein Bcl-XL. Furthermore, KA also enhanced the motility parameters, oxidative phosphorylation level, adenosine triphosphate level, and protein tyrosine phosphorylation of capacitated sperm, while preserving the acrosome integrity and plasma membrane integrity of capacitated sperm. In conclusion, this study offers new insights into the molecular mechanism of how KA inhibits porcine sperm apoptosis and improves capacitated sperm parameters. Additionally, it suggests that KA can serve as an alternative to antibiotics.

Proteomic analysis of boar seminal plasma: Putative markers for fertility based on capacity of semen preservation at 17°C

Boar seminal plasma (SP) proteins were associated with differences on sperm resistance to cooling at 17°C. However, information about seminal plasma proteins in boars classified by capacity of semen preservation and in vivo fertility remains lacking. Thus, the objective was to evaluate the SP proteome in boars classified by capacity of semen preservation and putative biomarkers for fertility. The ejaculates from high-preservation (HP) showed higher progressive motility during all 5 days than the low-preservation (LP) boars. There was no difference for farrowing rate between ejaculates from LP (89.7%) and HP boars (88.4%). The LP boars presented lower total piglets born (14.0 ± 0.2) than HP (14.8 ± 0.2; p < 0.01). A total of 257 proteins were identified, where 184 were present in both classes of boar, and 41 and 32 were identified only in LP and HP boars, respectively. Nine proteins were differently expressed: five were more abundant in HP (SPMI, ZPBP1, FN1, HPX, and C3) and four in LP boars (B2M, COL1A1, NKX3-2, and MPZL1). The HP boars had an increased abundance of SP proteins related to sperm resistance and fecundation process which explains the better TPB. LP boars had a higher abundance of SP proteins associated with impaired spermatogenesis.

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.

The natural flavonoid compound deguelin suppresses sperm (Sus Scrofa) functions through abnormal activation of the PI3K/AKT pathway

Deguelin is a natural flavonoid extracted from plants belonging to the Lonchocarpus, Derris, or Tephrosia genera. It inhibits AKT activity in tumors and has the potential to be used as a treatment for malignant tumors. However, the risks associated with the use of deguelin on male fertility have not yet been explained in detail. Therefore, this study was conducted to investigate the effects of deguelin on sperm functions during capacitation. First, boar spermatozoa were exposed to different concentrations of deguelin (0.1, 1, 10, 50, and 100 μM). Next, sperm functional assessments, such as sperm motility, capacitation status, intracellular ATP level, and cell viability, were performed. The expression levels of PI3K/AKT-related proteins and the phosphorylation of their tyrosine residues were also evaluated by western blotting. No significant difference was observed in cell viability; however, deguelin considerably decreased sperm motility and motion kinematics in a dose-dependent manner. Although no significant difference was observed in the capacitation status, acrosome reaction decreased at high concentrations of deguelin (50 and 100 μM). Furthermore, intracellular ATP levels were significantly decreased in all deguelin treatment groups compared with those in the control group. Results of western blotting revealed that deguelin substantially diminished tyrosine phosphorylation. Interestingly, in contrast to previous studies showing that deguelin inhibits AKT activity, our results showed that it increased the expression of PI3K/AKT pathway-related proteins. Collectively, these findings indicate that deguelin exerts negative effects on sperm functions due to abnormal PI3K/AKT signaling activation. We believe that this is the first study to provide evidence that deguelin can regulate sperm functions independent of PI3K/AKT pathway inhibition. Furthermore, its detrimental effects on male fertility should be considered while developing or using deguelin as a therapeutic agent.

Boar fertility is controlled through systematic changes of mitochondrial protein expression during sperm capacitation

Vigorous activation of mitochondria in spermatozoa during capacitation induces the biological and morphological changes of spermatozoa to acquire fertilizing ability. To in-depth understand the dynamic roles of mitochondrial and male fertility, this study was to identify how the mitochondrial proteins are changed during sperm capacitation and regulate male fertility using boar spermatozoa. The mitochondrial proteins were differentially changed during sperm capacitation according to fertility status, i.e., superior litter size (SL) and normal litter size (NL). Following sperm capacitation, ubiquitin-cytochrome c reductase core protein (UQCRC1) and ATP synthase F1 (ATP5F1) increased in NL, while cytochrome c oxidase subunit 5B (COX5B), and cytochrome c1 (CYC1) proteins decreased. In contrast, only and ubiquinone oxidoreductase core subunit 8 (NDUFS8) protein was increased in SL following capacitation. The protein expression difference value of CYC1, COX5B, and NDUFS8 following sperm capacitation was lower in NL than SL boars. Based on these complicated changes during sperm capacitation, the accuracy for predicting male fertility of NDUFS8 was increased to 87 %. Overall, considering the systematic orchestration of mitochondrial protein expression according to sperm capacitation status, it will be possible to better understand male fertility.

Mitochondrial Proteome Changes in Rett Syndrome

Rett syndrome (RTT) is a genetic neurodevelopmental disorder with mutations in the X-chromosomal MECP2 (methyl-CpG-binding protein 2) gene. Most patients are young girls. For 7-18 months after birth, they hardly present any symptoms; later they develop mental problems, a lack of communication, irregular sleep and breathing, motor dysfunction, hand stereotypies, and seizures. The complex pathology involves mitochondrial structure and function. Mecp2^-/y hippocampal astrocytes show increased mitochondrial contents. Neurons and glia suffer from oxidative stress, a lack of ATP, and increased hypoxia vulnerability. This spectrum of changes demands comprehensive molecular studies of mitochondria to further define their pathogenic role in RTT. Therefore, we applied a comparative proteomic approach for the first time to study the entity of mitochondrial proteins in a mouse model of RTT. In the neocortex and hippocampus of symptomatic male mice, two-dimensional gel electrophoresis and subsequent mass-spectrometry identified various differentially expressed mitochondrial proteins, including components of respiratory chain complexes I and III and the ATP-synthase FoF1 complex. The NADH-ubiquinone oxidoreductase 75 kDa subunit, NADH dehydrogenase [ubiquinone] iron-sulfur protein 8, NADH dehydrogenase [ubiquinone] flavoprotein 2, cytochrome b-c1 complex subunit 1, and ATP synthase subunit d are upregulated either in the hippocampus alone or both the hippocampus and neocortex of Mecp2^-/y mice. Furthermore, the regulatory mitochondrial proteins mitofusin-1, HSP60, and 14-3-3 protein theta are decreased in the Mecp2^-/y neocortex. The expressional changes identified provide further details of the altered mitochondrial function and morphology in RTT. They emphasize brain-region-specific alterations of the mitochondrial proteome and support the notion of a metabolic component of this devastating disorder.

Sperm capacitation as a predictor of boar fertility

Prediction of a boar's fertility level has great economic importance for sow herds. After standard sperm morphology and motility metrics are met, approximately 25% of boars have less than 80% conception rates. Due in part to the many factors involved in the fertilization process, a multifactorial model incorporating multiple relevant sperm physiology factors will likely lead to increased understanding of boar fertility. Here we review the current literature on boar sperm capacitation as a predictor of boar fertility. While limited, several studies have provided correlations between the percentage of sperm in an ejaculate that are capable of undergoing sperm capacitation in a chemically defined media and artificial insemination field fertility as well as proteome and other methods. Work summarized here underscores the need for further understanding of boar fertility.

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.

Integration of omics studies indicates that species-dependent molecular mechanisms govern male fertility

BACKGROUND

Comparative and comprehensive omics studies have recently been conducted to provide a comprehensive understanding of the biological mechanisms underlying infertility. However, because these huge omics datasets often contain irrelevant information, editing strategies for summarizing and filtering the data are necessary prerequisite steps for identifying biomarkers of male fertility. Here, we attempted to integrate omics data from spermatozoa with normal and below-normal fertility from boars and bulls, including transcriptomic, proteomic, and metabolomic data. Pathway enrichment analysis was conducted and visualized using g:Profiler, Cytoscape, EnrichmentMap, and AutoAnnotation to determine fertility-related biological functions according to species.

RESULTS

In particular, gamete production and protein biogenesis-associated pathways were enriched in bull spermatozoa with below-normal fertility, whereas mitochondrial-associated metabolic pathways were enriched in boar spermatozoa with normal fertility. These results indicate that below-normal fertility may be determined by aberrant regulation of protein synthesis during spermatogenesis, and the modulation of reactive oxygen species generation to maintain capacitation and the acrosome reaction governs boar sperm fertility.

CONCLUSION

Overall, this approach demonstrated that distinct molecular pathways drive sperm fertility in mammals in a species-dependent manner. Moreover, we anticipate that searching for species-specific signaling pathways may aid in the discovery of fertility-related biomarkers within large omics datasets.

Prediction of male fertility using Ras-related proteins

Identifying effective biomarkers for the diagnosis of male fertility is crucial for improving animal production and treating male infertility in humans. Ras-related proteins (Rab) are associated with morphological and motion kinematic functions in spermatozoa. Moreover, Rab2A, a Rab protein, is a possible male fertility-related biomarker. The present study was designed to identify additional fertility-related biomarkers among the various Rab proteins. First, the expression of Rab proteins (Rab3A, 4, 5, 8A, 9, 14, 25, 27A, and 34A) from 31 duroc boar spermatozoa was measured before and after capacitation; correlation between Rab protein expression and litter size was evaluated by statistical analysis. The results showed that the expression of Rab3A, 4, 5, 8A, 9, and 25 before capacitation and Rab3A, 4, 5, 8A, 9, and 14 after capacitation were negatively correlated with litter size. Moreover, depending on the cut-off values calculated by receiver operating curves, an increase in litter size was observed when evaluating the ability of the Rab proteins to forecast litter size. Therefore, we suggest that Rab proteins may be potential fertility-related biomarkers that could help select superior sires in the livestock industry.

Localization Patterns of RAB3C Are Associated with Murine and Human Sperm Formation

Background and Objectives: Septins (SEPTs) are highly conserved GTP-binding proteins and the fourth component of the cytoskeleton. Polymerization of SEPTs contributes to several critical cellular processes such as cytokinesis, cytoskeletal remodeling, and vesicle transportation. In our previous study, we found that SEPT14 mutations resulted in teratozoospermia with >87% sperm morphological defects. SEPT14 interactors were also identified through proteomic assays, and one of the peptides was mapped to RAB3B and RAB3C. Most studies on the RAB3 family have focused on RAB3A, which regulates the exocytosis of neurotransmitters and acrosome reactions. However, the general expression and patterns of the RAB3 family members during human spermatogenesis, and the association between RAB3 and teratozoospermia owing to a SEPT14 mutation, are largely unknown. Materials and Methods: Human sperm and murine male germ cells were collected in this study and immunofluorescence analysis was applied on the collected sperm. Results: In this study, we observed that the RAB3C transcripts were more abundant than those of RAB3A, 3B, and 3D in human testicular tissues. During human spermatogenesis, the RAB3C protein is mainly enriched in elongated spermatids, and RAB3B is undetectable. In mature human spermatozoa, RAB3C is concentrated in the postacrosomal region, neck, and midpiece. The RAB3C signals were delocalized within human spermatozoa harboring the SEPT14 mutation, and the decreased signals were accompanied by a defective head and tail, compared with the healthy controls. To determine whether RAB3C is involved in the morphological formation of the head and tail of the sperm, we separated murine testicular tissue and isolated elongated spermatids for further study. We found that RAB3C is particularly expressed in the manchette structure, which assists sperm head shaping at the spermatid head, and is also localized at the sperm tail. Conclusions: Based on these results, we suggest that the localization of RAB3C proteins in murine and human sperm is associated with SEPT14 mutation-induced morphological defects in sperm.

Carboxypeptidase E protein regulates porcine sperm Ca2+ influx to affect capacitation and fertilization

Mammalian spermatozoa acquire their fertilizing ability in the epididymis, which is important for sperm maturation and capacitation. Carboxypeptidase E (CPE) is a prohormone-processing enzyme and sorting receptor that functions intracellularly. Recently, CPE was identified to exist in the seminal plasma. However, little is known about the effects of CPE on reproductive function. This study focused on the effects of CPE on sperm function and fertilization. Herein, CPE was identified to be localized in the boar sperm, testis, epididymis, accessory gonad and seminal plasma, with high expression found in the bulbourethral glands and cauda epididymis. Furthermore, compared with high motility spermatozoa, a decrease in CPE abundance was observed in low motile spermatozoa by Western blot analysis. The use of specific antibody to inhibit the CPE in spermatozoa led to a decrease in sperm motility, followed by an expected decrease in acrosome exocytosis and tyrosine phosphorylation in the capacitation process. These changes were accompanied by a decrease in intracellular Ca²⁺ ([Ca²⁺]_i) influx, which resulted in a significant decrease in the cleavage rate during in vitro fertilization (IVF). Based on these observations, we suggest that CPE might affect porcine sperm Ca²⁺ influx to participate in the regulation of sperm function during capacitation.

GRP78 plays a key role in sperm function via the PI3K/PDK1/AKT pathway

Glucose-regulated protein 78 (GRP78), which is commonly found in the endoplasmic reticulum (ER), is involved in stabilizing ER proteins and inducing the unfolded protein response. Furthermore, GRP78 is expressed on the surface of most common cancer cells, such as cells of breast, lung, liver, and prostate cancers, and plays a role in apoptosis and cell proliferation via the PI3K/PDK1/AKT signaling pathway. Therefore, various trials have been performed for evaluating cancer treatment by inhibiting GRP78. Moreover, GRP78 is expressed on the surface of spermatozoa; however, its role in spermatozoa physiology remains unclear. Therefore, this study was designed to investigate the effects of GRP78 on sperm function during capacitation and elucidate the underlying mechanisms. Boar spermatozoa were exposed to various concentrations of HA15, a GRP78 antagonist, and sperm kinematic parameters, capacitation status, cell viability, levels of PI3K/PDK1/AKT-pathway related proteins, and tyrosine phosphorylation were evaluated. GRP78 inhibition significantly decreased sperm motility, kinematic parameters, capacitated and acrosome-reacted spermatozoa counts, and cell viability. Moreover, GRP78 expression was significantly decreased in HA15-treated spermatozoa compared to that in the control group, and levels of PI3K/PDK1/AKT-pathway related proteins changed significantly. Furthermore, tyrosine phosphorylation was significantly altered in the HA15-treated group. The results of this study suggest that GRP78 inhibition in cancer therapy may negatively affect sperm function. These results lay a strong foundation for future studies aiming to identify the molecular mechanisms related to GRP78 in spermatozoa.

Selenoprotein TXNRD3 supports male fertility via the redox regulation of spermatogenesis

Thioredoxin/glutathione reductase (TXNRD3) is a selenoprotein composed of thioredoxin reductase and glutaredoxin domains. This NADPH-dependent thiol oxidoreductase evolved through gene duplication within the Txnrd family, is expressed in the testes, and can reduce both thioredoxin and glutathione in vitro; however, the function of this enzyme remains unknown. To characterize the function of TXNRD3 in vivo, we generated a strain of mice bearing deletion of Txnrd3 gene. We show that these Txnrd3 knockout mice are viable and without discernable gross phenotypes, and also that TXNRD3 deficiency leads to fertility impairment in male mice. We found that Txnrd3 knockout animals exhibited a lower fertilization rate in vitro, a sperm movement phenotype, and an altered thiol redox status in sperm cells. Proteomic analyses further revealed a broad range of substrates reduced by TXNRD3 during sperm maturation, presumably as a part of sperm quality control. Taken together, these results show that TXNRD3 plays a critical role in male reproduction via the thiol redox control of spermatogenesis.

Establishment of a male fertility prediction model with sperm RNA markers in pigs as a translational animal model

BACKGROUND

Male infertility is an important issue that causes low production in the animal industry. To solve the male fertility crisis in the animal industry, the prediction of sperm quality is the most important step. Sperm RNA is the potential marker for male fertility prediction. We hypothesized that the expression of functional genes related to fertilization will be the best target for male fertility prediction markers. To investigate optimum male fertility prediction marker, we compared target genes expression level and a wide range of field data acquired from artificial insemination of boar semen.

RESULTS

Among the genes related to acrosomal vesicle exocytosis and sperm-oocyte fusion, equatorin (EQTN), zona pellucida sperm-binding protein 4 (ZP4), and sperm acrosome membrane-associated protein 3 exhibited high accuracy (70%, 90%, and 70%, respectively) as markers to evaluate male fertility. Combinations of EQTN-ZP4, ZP4-protein unc-13 homolog B, and ZP4-regulating synaptic membrane exocytosis protein 1 (RIMS1) showed the highest prediction value, and all these markers are involved in the acrosome reaction.

CONCLUSION

The EQTN-ZP4 model was efficient in clustering the high-fertility group and may be useful for selection of animal that has superior fertility in the livestock industry. Compared to the EQTN-ZP4 model, the ZP4-RIMS1 model was more efficient in clustering the low-fertility group and may be useful in the diagnosis of male infertility in humans and other animals. The appointed translational animal model and established biomarker combination can be widely used in various scientific fields such as biomedical science.

Proteomic Analysis of Hypothalamus and Pituitary Gland in Pre and Postpubertal Brahman Heifers

The hypothalamus and the pituitary gland are directly involved in the complex systemic changes that drive the onset of puberty in cattle. Here, we applied integrated bioinformatics to elucidate the critical proteins underlying puberty and uncover potential molecular mechanisms from the hypothalamus and pituitary gland of prepubertal (n = 6) and postpubertal (n = 6) cattle. Proteomic analysis in the hypothalamus and pituitary gland revealed 275 and 186 differentially abundant (DA) proteins, respectively (adjusted p-value < 0.01). The proteome profiles found herein were integrated with previously acquired transcriptome profiles. These transcriptomic studies used the same tissues harvested from the same heifers at pre- and post-puberty. This comparison detected a small number of matched transcripts and protein changes at puberty in each tissue, suggesting the need for multiple omics analyses for interpreting complex biological systems. In the hypothalamus, upregulated DA proteins at post-puberty were enriched in pathways related to puberty, including GnRH, calcium and oxytocin signalling pathways, whereas downregulated proteins were observed in the estrogen signalling pathway, axon guidance and GABAergic synapse. Additionally, this study revealed that ribosomal pathway proteins in the pituitary were involved in the pubertal development of mammals. The reported molecules and derived protein-protein networks are a starting point for future experimental approaches that might dissect with more detail the role of each molecule to provide new insights into the mechanisms of puberty onset in cattle.

Heat shock protein family D member 1 in boar spermatozoa is strongly related to the litter size of inseminated sows

Background

Sperm quality evaluation is the logical first step in increasing field fertility. Spermatozoa contain cytoplasmic organelles and biomolecules known as sperm-intrinsic factors, which play key roles in sperm maturation, sperm-oocyte fusion, and embryo development. In particular, sperm membrane proteins [e.g., arginine vasopressin receptor 2, beta-actin, prohibitin, and heat shock protein family D member 1 (HSPD1)] and RNA could be used as functional indicators of male fertility. We sought to clarify the effects of differential mRNA expression of selected genes on several fertilisation parameters, including sperm motility, motion kinematics, capacitation, and litter size, in a porcine model.

Results

Our results demonstrated that HSPD1 expression was significantly correlated with male fertility, as measured by the litter size of inseminated sows. The expression of HSPD1 mRNA was linked to sperm motility and other motion kinematic characteristics. Furthermore, HSPD1 had a 66.7% overall accuracy in detecting male fertility, and the high-litter size group which was selected with the HSPD1 marker had a 1.34 greater litter size than the low-litter size group.

Conclusions

Our findings indicate that HSPD1 might be a helpful biomarker for superior boar selection for artificial insemination, which could boost field fertility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00689-0.

Ras-related proteins (Rab) play significant roles in sperm motility and capacitation status

Rab proteins are widely known for their involvement in establishing Golgi apparatus and controlling Golgi trafficking in eukaryotic cells. Specifically, Rab proteins play significant roles in acrosome formation and exocytosis. Furthermore, mechanisms involved in the regulation of Rab proteins during capacitation have been identified. However, there has been no direct evaluation to assess the correlation between Rab proteins and sperm function. Consequently, this study was designed to analyze the correlation between Rab proteins and sperm functions. Individually, we analyzed the sperm motility patterns, motion kinematics, capacitation status, and Rab protein expression levels of sperm samples from 31 boars before and after capacitation. As a result, we discovered that Rab3A, Rab5, Rab11, Rab14, and Rab27A correlated with various sperm motility patterns, motion kinematics before capacitation. Rab3A, Rab5, Rab11, Rab14, and Rab34 correlated with various sperm motility patterns, motion kinematics after capacitation. Moreover, Rab4 and Rab34 were associated with capacitation status before capacitation, and Rab3A, 25, and 27A correlated with capacitation status after capacitation. This is the first study to analyze the correlation between Rab proteins and sperm functions. Collectively, our results indicate that specific sperm motility and kinematics, as well as the structural condition of the sperm head and capacitation status, regulate individual Rab protein. Therefore, we expect that the current findings will be used to identify the etiology of idiopathic male infertility patients and to diagnose male fertility and that Rab proteins will be employed as biomarkers to predict and analyze male fertility.

Sperm proteins ODF2 and PAWP as markers of fertility in breeding bulls

Low fertility is the single most important factor limiting livestock reproductive performance, adversely affecting the cattle industry and causing millions of dollars of economic loss. In the livestock industry, male fertility is of crucial importance for the reproductive performance of livestock. However, there is a lack of reliable biomarkers to predict bull fertility in artificial insemination service. The objective of this study was to identify sperm proteins as biomarkers for bull fertility. To discover candidate sperm quality biomarkers, sperm proteome profiling was conducted in extreme high- and extreme low-fertile bulls selected from a pool of 1000 AI sires with varied fertility. Thirty-two differentially expressed proteins were identified. Among them, high levels of sperm outer dense fiber of sperm tails 2 (ODF2) and post-acrosomal assembly of sperm head protein (PAWP/WBP2NL) represented the most extreme differences in quantity between high- and low-fertility bulls. Protein immunodetection and flow cytometry used to validate these putative fertility markers in a combined cohort of 154 AI sires. Both ODF2 and PAWP correlated significantly with fertility. In conclusion, ODF2 and PAWP can be used to assess semen quality and predict sire fertility.

Proteomic profiling of cryopreserved Trichormus variabilis using various cryoprotectants

Algae, which may be unicellular or multicellular, can carry out photosynthesis just like plants as they effectively utilize light energy. They contain various physiologically active substances and are, therefore, widely used commercially to produce healthy food and feed additives, cosmetics, and energy supplements. For useful applications, the cryopreservation technique has been used in various fields. Recently, to develop suitable cryopreservation methods for algal applications, various studies have been performed. However, adequate investigations have not been conducted to understand the mechanism underlying algal cryopreservation at the molecular level. Therefore, this study examined the profile alteration of the proteome using cryopreservation with various cryoprotectants (CPAs). Trichormus variabilis was cultured and then cryopreserved with 10% dimethyl sulfoxide, methanol, and glycerol, after which, proteome profiling was done. Finally, signaling pathway search was performed, and a new signaling pathway was established based on differentially expressed proteins. As a result, the expression levels of 17 proteins were observed. Additionally, it was confirmed that the differentially expressed proteins were related to 16 signaling pathways and that they were capable of interacting with each other. The findings suggest that the differentially expressed proteins may be applied as biomarkers for algal cryopreservation and to understand the mechanism underlying T. variabilis cryopreservation. Moreover, it is anticipated that the results from this study would be useful in selecting suitable CPAs and in upgrading the cryopreservation techniques.

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

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

Peroxiredoxin 4 directly affects the male fertility outcome in porcine

Peroxiredoxins (Prdxs) are known to play a critical role in regulating male fertility as antioxidant enzymes. Although several studies have suggested a close association between Prdxs and male fertility, few studies have explored the efficacy of Prdxs to predict male fertility. Therefore, the current study was designed to discover the most efficient biomarkers among the Prdxs with six isoforms. Our study showed a significant positive correlation between the litter size and the levels of PRDX 4 among all isoforms in spermatozoa. Subsequently, a regression analysis using a combination of markers was conducted to increase efficacy for fertility prediction. Nevertheless, PRDX4 had the highest efficacy compared to other combination models to predict litter size. The prediction accuracy of male fertility was further evaluated through receiver operating characteristic curve analysis, which showed that PRDX 4 could predict the litter size with high overall accuracy of 95%. Moreover, litter size was increased by 1.55 piglets after predicting high litter size using PRDX 4. This is the first study to comprehensively elucidate the role of all isoforms of PRDXs on male fertility to the best of our knowledge. PRDX 4 was tested and evaluated up to a practical level. Data here reported suggesting PRDX 4 marker allowed the highest accuracy for male fertility prediction and diagnosis, leading to a measurable improvement in the male fertility outcome.

Investigation Into the Relationship Between Sperm Cysteine-Rich Secretory Protein 2 (CRISP2) and Sperm Fertilizing Ability and Fertility of Boars

The proteins in the seminal plasma and on the sperm surface play important roles in sperm function and numerous reproductive processes. The cysteine-rich secretory proteins (CRISPs) are enriched biasedly in the male reproductive tract of mammals, and CRISP2 is the sole member of CRISPs produced during spermatogenesis; whereas the role of CRISP2 in fertilization and its association with fertility of boars are still unclear. This study aimed to investigate the relationship between the sperm CRISP2 and boar fertility, and explore its impact sperm fertilizing ability. The levels of CRISP2 protein in sperm were quantified by ELISA; correlation analysis was performed to evaluate the association between CRISP2 protein levels and boar reproductive parameters. Meanwhile, the expression of CRISP2 in boar reproductive organs and sperm, and the effects of CRISP2 on in vitro fertilization (IVF) were examined. The results showed that boars with high sperm levels of CRISP2 had high fertility. The protein levels of CRISP2 in sperm were positively correlated with the litter size (r = 0.412, p = 0.026), the number of live-born piglets (r = 0.421, p = 0.023) and the qualified piglets per litter (r = 0.381, p = 0.042). CRISP2 is specifically expressed in the testis and sperm of adult boars, and its location on sperm changed mainly from the post-acrosomal region to the apical segment of acrosome during capacitation. The cleavage rate was significantly decreased by adding the anti-CRISP2 antibody to the IVF medium, which indicates CRISP2 plays a critical role in fertilization. In conclusion, CRISP2 protein is specifically expressed in the adult testis and sperm and is associated with sperm fertilizing ability and boar fertility. Further mechanistic studies are warranted, in order to fully decipher the role of CRISP2 in the boar reproduction.

Effects of Obesity and Diabetes on Sperm Cell Proteomics in Rats

Infertility caused by male factors is potentially associated with metabolic disorders such as obesity and/or diabetes. This experimental study was conducted in a male rodent model to assess the effects of different diseases on semen quality and sperm proteomics. Ten Wistar rats were used for each treatment. Rats were fed commercial food provided controllably to the control group and the diabetic group, and a hypercaloric diet supplemented with 5% sucrose in water was provided ad libitum to the obese group for 38 weeks. Diabetes was induced with 35 mg/kg streptozotocin. After euthanasia, testicles, spermatozoa, fat, and blood (serum) samples were collected. Spermatozoa were evaluated for quality and subjected to proteomics analyses. Histology and cytology of the testis, and serum leptin, adiponectin, interleukin 8 (IL-8), blood glucose, and testosterone levels, were also assessed. Body weight, retroperitoneal and testicular fat, and the Lee index were also measured. Obesity and diabetes were induced. The diabetic group showed noticeable changes in spermatogenesis and sperm quality. The mass spectrometry proteomics data have been deposited in Mendeley Data (doi: 10.17632/rfp7kfjcsd.5). Fifteen proteins varied in abundance between groups, especially proteins related to energy production and structural function of the spermatozoa, suggesting disturbances in energy production with a subsequent alteration in sperm motility in both groups, but with a compensatory response in the obese group.

L-amino acid oxidase 1 in sperm is associated with reproductive performance in male mice and bulls

Sperm quality is an important indicator of male fertility, and a suitable biomarker enables the selection of high-quality spermatozoa. We previously found that L-amino acid oxidase encoded by the L-amino acid oxidase 1 (Lao1) gene exerts biological roles in the mammary gland and brain by converting specific L-amino acids into keto acids, ammonia, and hydrogen peroxide (H2O2). Here, we describe the role of Lao1 in male reproduction. Lao1-deficient (Lao1-/-) male mice generated fewer pregnant embryos and pups as well as lower ratios of fertilized oocytes and even ovulated number was not different, suggesting that male subfertility caused the smaller litters. We found that LAO1 expressed in acrosomes is associated with high malformation ratios and low viability of Lao1-/- sperm. Wild-type (WT) sperm produced more H2O2 than Lao1-/- sperm, and 10 μM H2O2 restored knockout (KO) sperm viability in vitro. In addition, the sperm ratio of induced acrosome reaction was higher in WT than in Lao1-/- sperm incubated with the calcium ionophore A23187. Moreover, LAO1 expression was abundant in bovine sperm with high fertilization ratios. We concluded that LAO1 localized in the sperm acrosome influences sperm viability and morphology as well as the acrosome reaction, and that LAO1-deficient sperm might cause male subfertility. Thus, LAO1 might serve as a novel marker for selecting high-quality spermatozoa, especially for livestock reproduction.

Analysis of differentially abundant proteins related to boar fertility in seminal plasma using iTRAQ-based quantitative proteomics

Animal fertility is one of the most important characteristics for the livestock breeding industry. Conventional semen analysis provides basic information on sperm quality, but the predictive value of such analysis with regard to fertility remains questionable. Therefore, it is important to determine and predict male fertility more accurately in the clinic. To identify seminal plasma proteins involved in fertility, isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography with tandem mass spectrometry (quantitative proteomic analysis) were used to identify differentially abundant proteins (DAPs) in seminal plasma between high- and low-reproductive-efficiency Landrace boars. A total of 141 DAPs were identified, of which 125 upregulated and 16 downregulated proteins were subjected to bioinformatics analysis. These DAPs were found to be mainly involved in proteolysis, ATP binding, and energy metabolism. We investigated the relevance of three DAPs-ceruloplasmin, carboxypeptidase E (CPE), and serpin family A member 12 (SERPINA12)-in an in vitro fertility assay. This assay revealed that the inhibition of these proteins with antibodies can reduce or increase the fertilization rate. These results indicate possible biomarkers for the selection of high-fertility boars and provide a theoretical basis for the use of protein biomarkers in the livestock breeding industry. SIGNIFICANCE: Our study identified differentially abundant proteins in the seminal plasma of high-reproductive-efficiency and low-reproductive-efficiency Landrace boars. These proteins may be used as biomarkers to screen out high-fertility boars. The study can provide not only a new method for improving the effects of artificial insemination and reproductive efficiency of boars but also an important reference for boar breeding. Meanwhile, because pigs and humans have similar physiological parameters and organ sizes, our findings can also serve as a reference for human reproduction research.

Mitochondrial Functionality in Male Fertility: From Spermatogenesis to Fertilization

Mitochondria are structurally and functionally distinct organelles that produce adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS), to provide energy to spermatozoa. They can also produce reactive oxidation species (ROS). While a moderate concentration of ROS is critical for tyrosine phosphorylation in cholesterol efflux, sperm–egg interaction, and fertilization, excessive ROS generation is associated with male infertility. Moreover, mitochondria participate in diverse processes ranging from spermatogenesis to fertilization to regulate male fertility. This review aimed to summarize the roles of mitochondria in male fertility depending on the sperm developmental stage (from male reproductive tract to female reproductive tract). Moreover, mitochondria are also involved in testosterone production, regulation of proton secretion into the lumen to maintain an acidic condition in the epididymis, and sperm DNA condensation during epididymal maturation. We also established the new signaling pathway using previous proteomic data associated with male fertility, to understand the overall role of mitochondria in male fertility. The pathway revealed that male infertility is associated with a loss of mitochondrial proteins in spermatozoa, which induces low sperm motility, reduces OXPHOS activity, and results in male infertility.

New technique of sex preselection for increasing female ratio in boar sperm model

In this study, we tried to optimize the porcine semen extender conditions to maximize the differences between live X chromosome-bearing (X) spermatozoa and to Y chromosome-bearing (Y) spermatozoa without a decline in the fertility rate at different pH conditions during storage. We observed the viability of X and Y boar spermatozoa in acidic (pH 6.2), original (pH 7.2), and alkaline condition (pH 8.2) for 5 days to investigate the effect of storage conditions on the X to Y spermatozoa ratio. The functional parameters of spermatozoa were also examined to evaluate sperm quality. Sperm motility was preserved at pH 7.2 and pH 6.2 for 3 days, while sperm motility at pH 8.2 decreased significantly after 2 days. Non-capacitated spermatozoa increased while capacitated spermatozoa decreased during storage. Sperm viability decreased significantly duration-dependent under all pH conditions, but there was no significant difference during storage at pH 6.2 and 7.2. The X: Y ratio of live spermatozoa in acidic condition was maximized (1.2:1) without affecting the sperm function and fertility-related protein expression after 2 days compared to original conditions. Moreover, insemination of sows using acidic extender increased the number of female pups on days 1 and 2 of preservation. These results indicate that the production of female offspring may increase when acidic BTS is used for 2 days without affecting the success rate of AI. Above all, this method is simple and economical compared to other methods.

Phosphoproteomics and Bioinformatics Analyses Reveal Key Roles of GSK-3 and AKAP4 in Mouse Sperm Capacitation

Protein phosphorylation can induce signal transduction to change sperm motility patterns during sperm capacitation. However, changes in the phosphorylation of sperm proteins in mice are still incompletely understood. Here, capacitation-related phosphorylation in mouse sperms were firstly investigated by label-free quantitative (LFQ) phosphoproteomics coupled with bioinformatics analysis using ingenuity pathway analysis (IPA) methods such as canonical pathway, upstream regulator, and network analysis. Among 1632 phosphopeptides identified at serine, threonine, and tyrosine residues, 1050 novel phosphosites, corresponding to 402 proteins, were reported. Gene heatmaps for IPA canonical pathways showed a novel role for GSK-3 in GP6 signaling pathways associated with capacitation for 60 min. At the same time, the reduction of the abundant isoform-specific GSK-3α expression was shown by western blot (WB) while the LFQ pY of this isoform slightly decreased and then increased. The combined results from WB and LFQ methods explain the less inhibitory phosphorylation of GSK-3α during capacitation and also support the predicted increases in its activity. In addition, pAKAP4 increased at the Y156 site but decreased at the Y811 site in a capacitated state, even though IPA network analysis and WB analysis for overall pAKAP revealed upregulated trends. The potential roles of GSK-3 and AKAP4 in fertility are discussed.

Identification of new protein biomarkers associated with the boar fertility using iTRAQ-based quantitative proteomic analysis

In this study, we performed the isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis in the spermatozoa of Landrace boars with different fertility potentials and investigated the ability of sperm acrosome associated 4 (SPACA4) and IZUMO family member 2 (IZUMO2) to predict the reproductive perform of boars. The iTRAQ results revealed that 202 proteins were up-regulated and 43 proteins were down-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 protein levels were significantly up-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 expression were specifically detected in the adult boar testis. SPACA4 levels were positively correlated with Sow's farrowing rate and reproductive efficiency, but not litter size. IZUMO2 were positively correlated with litter size, Sow's farrowing rate and reproductive efficiency. Treating the boar semen with SPACA4 or IZUMO2 antibodies for 30 min and 60 min failed to affect the sperm motility; while treating the semen with SPACA4 antibody significantly reduced the fertilization and cleavage rates. Similar results for fertilization and cleavage rates were found in IZUMO2 antibody-treated semen. Collectively, our results indicated that protein levels of SPACA4 and IZUMO2 in the spermatozoa were positively related to the reproductive performance of Landrace boars.

Bioinformatics approaches for improving seminal plasma proteome analysis

Reproduction efficiency of male animals is one of the key factors influencing the sustainability of livestock. Mass spectrometry (MS) based proteomics has become an important tool for studying seminal plasma proteomes. In this review, we summarize bioinformatics analysis strategies for current proteomics approaches, for identifying novel biomarkers of reproductive robustness.

Uncovering sperm metabolome to discover biomarkers for bull fertility

Background

Subfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows. Variation in bull fertility has been demonstrated even among those animals exhibiting normal sperm numbers, motility, and morphology. Despite advances in research, molecular and cellular mechanisms underlying the causes of low fertility in some bulls have not been fully elucidated. In this study, we investigated the metabolic profile of bull spermatozoa using non-targeted metabolomics. Statistical analysis and bioinformatic tools were employed to evaluate the metabolic profiles high and low fertility groups. Metabolic pathways associated with the sperm metabolome were also reported.

Results

A total of 22 distinct metabolites were detected in spermatozoa from bulls with high fertility (HF) or low fertility (LF) phenotype. The major metabolite classes of bovine sperm were organic acids/derivatives and fatty acids/conjugates. We demonstrated that the abundance ratios of five sperm metabolites were statistically different between HF and LF groups including gamma-aminobutyric acid (GABA), carbamate, benzoic acid, lactic acid, and palmitic acid. Metabolites with different abundances in HF and LF bulls had also VIP scores of greater than 1.5 and AUC- ROC curves of more than 80%. In addition, four metabolic pathways associated with differential metabolites namely alanine, aspartate and glutamate metabolism, β-alanine metabolism, glycolysis or gluconeogenesis, and pyruvate metabolism were also explored.

Conclusions

This is the first study aimed at ascertaining the metabolome of spermatozoa from bulls with different fertility phenotype using gas chromatography-mass spectrometry. We identified five metabolites in the two groups of sires and such molecules can be used, in the future, as key indicators of bull fertility.

Levels of activity of superoxide dismutase in seminal plasma do not predict fertility of pig AI-semen doses

Superoxide dismutase (SOD) is a major antioxidant enzyme in boar seminal plasma (SP). This study evaluated how SP-SOD affected sperm attributes when semen of boars of various breeds, included in commercial artificial insemination (AI)-programs, was extended and liquid-stored at 17 °C for AI; as well as their in vivo fertility (farrowing rate and litter size of 10,952 AI-sows). SP-SOD-activity was assessed in 311 ejaculates (100 boars) while sperm motility (by CASA), viability and intracellular H₂O₂ generation in viable spermatozoa (by flow cytometry) were measured at 0 and 72 h of liquid storage. SP-SOD activity was not affected by breed but differed (P < 0.001) between boars (n = 50), ranging from 1.16 ± 0.11 to 7.02 ± 0.75 IU/mL. Semen AI-doses (n = 44) hierarchically grouped (P < 0.001) with low SP-SOD activity showed lower (P < 0.05) sperm motility and intracellular H₂O₂ at 72 h of liquid storage. Fertility did not differ between AI-boars (n = 39) hierarchically grouped (P < 0.001) with high or low SP-SOD activity. In conclusion, SP-SOD activity is boar dependent and positively related with sperm functionality of liquid-stored semen AI-doses. However, this positive effect is not reflected on in vivo fertility post-AI.

Porcine seminal protein-I and II mRNA expression in boar spermatozoa is significantly correlated with fertility

In recent years, genomic and proteomic biomarkers have been identified for the diagnosis of male fertility to overcome the limitations of conventional semen analysis. Owing to the limited genes available so far, the single gene approach is commonly adopted for analyzing the phenotype of interest. However, the single-gene approach is less effective than multiple-gene strategies for diagnosing a desirable phenotype. Herein, we investigate the ability of two fertility-related genomic markers (porcine seminal protein (PSP)-I and PSP-II) in spermatozoa to predict boar litter size in addition to conventional semen parameters. First, we examined different semen parameters (motility, motion kinematics, and capacitation status) and gene expression in high- and low-litter size boar spermatozoa. Then, we evaluated the correlation of these parameters with the fertility of 21 Yorkshire boars. Finally, we investigated the efficacy of single/combined markers to predict male fertility using a comprehensive statistical model. Our result showed that there were no significant differences in sperm motility, motion kinematics, or capacitation status, however, the mRNA expression of PSP-I and PSP-II in spermatozoa was significantly different in high- and low-litter size boars. In the individual screening test, the expression of both genes was negatively correlated with boar fertility (r = 0-0.578 and -0.456, respectively), whereas only hyperactivation (HYP) showed a positive correlation (r = 0.444) among the tested semen parameters. As single markers, PSP-I and PSP-II have a better diagnostic power to predict boar fertility, regardless of HYP, in quality assessment analyses. In addition, when these markers were combined, the positive predictive value, negative predictive value, and overall test effectiveness for fertility detection were improved. Surprisingly, when PSP-I and PSP-II were considered together, the deviation of the predicted average litter size between high- and low-litter size boars was 1.77. Based on the findings, we suggest that the use of genomic markers in spermatozoa rather than commonly analyzed semen parameters may be more accurate for evaluating male fertility. Moreover, using a combination of markers could increase the overall accuracy of (in)fertility predictions, and thus, could be considered for field application.

NT5C1B and FH are closely associated with cryoprotectant tolerance in spermatozoa

BACKGROUND

Cryoprotective agent (CPA) addition during sperm cryopreservation causes detrimental effects on sperm function and quality. We previously reported that CPA addition adversely affects bull sperm physiological functions and shows differentially expressed proteins.

OBJECTIVES

To study functional and proteomic alterations between high CPA-tolerant spermatozoa (HCS) and low CPA-tolerant spermatozoa (LCS) in bull.

MATERIALS AND METHODS

Bull semen was collected from the cauda epididymides of Korean bull (Hanwoo) and suspended in Tris-egg yolk buffer (TYB). The collected fresh semen was diluted down to a final concentration of 6% glycerol TYB solution. After CPA exposure to the sperm cells from individual bulls, the percentage of sperm motility was examined by utilizing a computer-assisted sperm analysis system. According to sperm motility value, the HCS (motility above 80%) and LCS (motility below 60%) groups were evaluated for sperm function parameters (swimming speed, capacitation, viability, and mitochondrial function) and protein expression.

RESULTS

The HCS group had good sperm function parameters following CPA addition, whereas sperm functions in the LCS group were significantly reduced. There were differentially expressed proteins between the HCS and LCS groups. Cytosolic 5-nucleotidase 1B and fumarate hydratase were abundantly expressed in the HCS group, while F-actin-capping protein subunit beta, voltage-dependent anion-selective channel protein 2, and cytochrome b-c1 complex subunit 1 had a lower expression in the HCS group than in the LCS group.

DISCUSSION AND CONCLUSION

Identified proteins implicate potential markers to predict CPA-tolerable spermatozoa, which could provide a method of selecting animals and breeds with cryoprotectant resistance.

Boar semen proteomics and sperm preservation

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

The calcium-sensing receptor regulates protein tyrosine phosphorylation through PDK1 in boar spermatozoa

Regulation of protein tyrosine phosphorylation is required for sperm capacitation and oocyte fertilization. The objective of the present work was to study the role of the calcium-sensing receptor (CaSR) on protein tyrosine phosphorylation in boar spermatozoa under capacitating conditions. To do this, boar spermatozoa were incubated in Tyrode's complete medium for 4 hr and the specific inhibitor of the CaSR, NPS2143, was used. Also, to study the possible mechanism(s) by which this receptor exerts its function, spermatozoa were incubated in the presence of specific inhibitors of the 3-phosphoinositide dependent protein kinase 1 (PDK1) and protein kinase A (PKA). Treatment with NPS2143, GSK2334470, an inhibitor of PDK1 and H-89, an inhibitor of PKA separately induced an increase in tyrosine phosphorylation of 18 and 32 kDa proteins, a decrease in the serine/threonine phosphorylation of the PKA substrates together with a drop in sperm motility and viability. The present work proposes a new signalling pathway of the CaSR, mediated by PDK1 and PKA in boar spermatozoa under capacitating conditions. Our results show that the inhibition of the CaSR induces the inhibition of PDK1 that blocks PKA activity resulting in a rise in tyrosine phosphorylation of p18 and p32 proteins. This novel signalling pathway has not been described before and could be crucial to understand boar sperm capacitation within the female reproductive tract.

Seminal plasma proteins and their relationship with sperm motility and morphology in boars

The identification of biomarkers associated with seminal traits could aid in the selection of higher quality ejaculates and benefit the swine industry. The objective of this study was to identify boar seminal plasma proteins associated with sperm motility and morphology. Twenty ejaculates from fifteen adult boars from a commercial boar stud were used for this work. After routine semen collection and analysis, ejaculates were classified into two groups: high-quality semen (HQS) and low-quality semen (LQS), based on sperm motility and morphology. Semen samples were processed for seminal plasma separation and analysis by 2D SDS-PAGE. Total and progressive sperm motility differed between groups (p < 0.001), as well sperm morphology (p < 0.05). The intensity of spots identified as Major seminal plasma PSP-I (PSP-I) and cathepsin B (CTSB) was higher in LQS as compared to HQS samples (p < 0.05). Also, PSP-I was positively associated with major and sperm cauda defects. Sperm motility was negatively correlated with both PSP-I and cathepsin B. We conclude that high concentrations of Major seminal plasma PSP-I and cathepsin B in boar seminal plasma are associated with reduced total and progressive sperm motility and low sperm morphology and might be used as biomarkers for semen quality.