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

An updated review on the application of proteomics to explore sperm cryoinjury mechanisms in livestock animals

This comprehensive review critically examines the application of proteomics in understanding sperm cryoinjury mechanisms in livestock animals, in the context of the widespread use of semen cryopreservation for genetic conservation. Despite its global adoption, cryopreservation often detrimentally affects sperm quality and fertility due to cryoinjuries. These injuries primarily arise from ice crystal formation, osmotic shifts, oxidative stress, and the reorganization of membrane proteins and lipids during freezing and thawing, leading to premature capacitation-like changes. Moreover, the cryopreservation process induces proteome remodeling in mammalian sperm. Although there have been technological advances in semen cryopreservation, the precise mechanisms of mammalian sperm cryoinjury remain elusive. This review offers an in-depth exploration of how recent advancements in proteomic technologies have enabled a detailed investigation into these molecular disruptions. It presents an analysis of protein-level alterations post-thaw and their impact on sperm viability and functionality. Additionally, it discusses the role of proteomics in refining cryopreservation techniques to mitigate cryoinjury and enhance reproductive outcomes in livestock. This work synthesizes current knowledge, highlights gaps, and suggests directions for future research in animal reproductive science and biotechnology.

Protein Identification of Seminal Plasma in Bali Bull (Bos javanicus)

The purpose of this study was to identify seminal plasma proteins in Bali bull and their potential as biomarkers of fertility. Semen was collected from 10 bulls aged 5-10 years using an artificial vagina. Fresh semen was then centrifuged (3000× g for 30 min). The supernatant was put into straws and stored in liquid nitrogen. The semen plasma protein concentration was determined using the Bradford method, and the protein was characterized using 1D-SDS-PAGE. Coomassie Brilliant Blue (CBB) was used to color the gel, and the molecular weight of the protein was determined using PM2700. A total of 94 proteins were identified in the seminal plasma of Bali bulls analyzed using LC-MS/MS (liquid chromatography-mass spectrometry). Proteins spermadhesin 1 (SPADH1), C-type natriuretic peptide (NPPC), clusterin (CLU), apoliprotein A-II (APOA2), inositol-3-phosphate synthase 1 (ISYNA1), and sulfhydryl oxidase 1 (QSOX1) were identified as important for fertility in Bos javanicus. These proteins may prove to be important biomarkers of fertility in Bali bulls. These proteins are important for reproductive function, which includes spermatozoa motility, capacitation, and acrosome reactions. This study provides new information about the protein content in seminal plasma in Bali bulls. The LC-MS/MS-based proteome approach that we applied in this study obtained 94 proteins. The identification of these seminal plasma proteins of Bali bulls and their potential as fertility biomarkers may have an impact on the success of future artificial insemination (AI).

Proteomic analysis of spermatozoa reveals caseins play a pivotal role in preventing short-term periods of subfertility in stallions

Stallions experience transient fluctuations in fertility throughout the breeding season. Considering pregnancy diagnoses cannot be ascertained until ~14 days post-breeding, the timely detection of decreases in stallion fertility would enhance industry economic and welfare outcomes. Therefore, this study aimed to identify the proteomic signatures reflective of short-term fertility fluctuations, and to determine the biological mechanisms governing such differences. Using LC–MS/MS, we compared the proteomic profile of semen samples collected from commercially “fertile” stallions, during high- and low-fertility periods. A total of 1702 proteins were identified, of which, 38 showed a significant change in abundance (p ≤ 0.05). Assessment of intra- and inter-stallion variability revealed that caseins (namely κ-, α-S1-, and α-S2-casein), were significantly more abundant during “high-fertility” periods, while several epididymal, and seminal plasma proteins (chiefly, epididymal sperm binding protein 1 [ELSPbP1], horse seminal plasma protein 1 [HSP-1] and clusterin), were significantly more abundant during “low-fertility” periods. We hypothesised that an increased abundance of caseins offers greater protection from potentially harmful seminal plasma proteins, thereby preserving cell functionality and fertility. In vitro exposure of spermatozoa to casein resulted in decreased levels of lipid scrambling (Merocyanine 540), higher abundance of sperm-bound caseins (α-S1-, α-S2-, and κ-casein), and lower abundance of sperm-bound HSP-1 (p ≤ 0.05). This study demonstrates key pathways governing short-term fertility fluctuations in the stallion, thereby providing a platform to develop robust, fertility assessment strategies into the future.

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.

ProAKAP4 as Novel Molecular Marker of Sperm Quality in Ram: An Integrative Study in Fresh, Cooled and Cryopreserved Sperm

To improve artificial insemination protocols in ovine species it is crucial to optimize sperm quality evaluation after preservation technologies. Emerging technologies based on novel biomolecules and related to redox balance and proteins involved in sperm motility such as ProAKAP4 could be successfully applied in ram sperm evaluation. In this work, a multiparametric analysis of fresh, cooled, and cryopreserved ram sperm was performed at different complexity levels. Samples were evaluated in terms of motility (total motility, progressive motility, and curvilinear velocity), viability, apoptosis, content of reactive oxygen species, oxidation‒reduction potential, and ProAKAP4 expression and concentration. As expected, cryopreserved samples showed a significant decrease of sperm quality (p < 0.05), evidencing different freezability classes among samples that were detected by ProAKAP4 analyses. However, in cooled sperm no differences were found concerning motility, viability, apoptosis, ROS content, and redox balance compared to fresh sperm that could explain the reported decrease in fertility rates. However, although the proportion of sperm ProAKAP4 positive-cells remained unaltered in cooled sperm compared to fresh control, the concentration of this protein significantly decreased (p < 0.05) in cooled samples. This altered protein level could contribute to the decrease in fertility rates of cooled samples detected by some authors. More importantly, ProAKAP4 can be established as a promising diagnostic parameter of sperm quality allowing us to optimize sperm conservation protocols and finally improve artificial insemination in ovine species.

Butylated hydroxytoluene protects bull sperm surface protein-P25b in different extenders following cryopreservation

Aim

The aim of this study was to investigate the effects of different concentration of butylated hydroxytoluene (BHT) on sperm membrane surface protein "P25b" from cryopreserved bull semen in either lecithin based Bioxcell^® (BX) or two egg-yolk based extenders, tris-egg yolk (TEY), and citrate-egg yolk (CEY).

Materials and Methods

Forty-five semen samples, 15 each were extended with either BX, TEY, or CEY extender which contained different concentrations (0.0 - control, 0.5, 1.0, 1.5, 2.0, and 3.0 mM/mL) of BHT. The extended semen samples were frozen at a concentration of 20×10⁶/mL in 0.25 mL straws and stored in liquid nitrogen for 2weeks. The frozen samples were thereafter thawed, proteins extracted and analyzed for quantities of protein P25b through direct sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel densitometry. Peptides were confirmed by Western blotting (WB).

Results

Results showed that supplementation of BHT improved (p<0.05) quantity of protein P25b at concentrations of 0.5mM/mL for BX and at 1.0 mM/mL for TEY and CE when compared with the controls and other treatments.

Conclusion

BHT supplementation at 0.5 in BX and 1.0 mM/mL in TEY and CEY has protected bull sperm fertility marker protein P25b in frozen-thawed bull sperm.

Seminal plasma proteomes and sperm fertility

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

Rabbit seminal plasma proteome: The importance of the genetic origin

The present study was conducted to characterise rabbit seminal plasma proteins (SP proteins) focusing on the influence of the genetic origin and seasonality. In addition, β-NGF protein quantity in SP was determined. Semen samples were recovered from January to December 2014 using 6 males belonging to genotype A and six from genotype R. For each genotype, one pooled sample at the beginning, middle and end of each season was selected to develop the experiment. A total of 24 pools (3 for each season and genetic line) were analysed. SP proteins of the two experimental groups were recovered and subjected to in-solution digestion nano LC-MS/MS and bioinformatics analysis. The resulting library included 402 identified proteins validated with ≥95% Confidence (unused Score ≥ 1.3). These data are available via ProteomeXchange with identifier PXD006308. Only 6 proteins were specifically implicated in reproductive processes according to Gene Ontology annotation. Twenty-three proteins were differentially expressed between genotypes, 11 over-expressed in genotype A and 12 in genotype R. Regarding the effect of season on rabbit SP proteome, results showed that there is no clear pattern of protein variation throughout the year. Similar β-NGF relative quantity was observed between seasons and genotypes. In conclusion, this study generates the largest library of SP proteins reported to date in rabbits and provides evidence that genotype is related to a specific abundance of SP proteins.

Analysis of seminal plasma from brown bear (Ursus arctos) during the breeding season: Its relationship with testosterone levels

Seminal plasma (SP) plays an important role in the motility, viability and maintenance of the fertilizing capacity of mammalian spermatozoa. This study is the first on brown bear (Ursus arctos) SP components, and has two main objectives: 1) to define the SP composition in bear ejaculate and 2) to identify variations in SP composition in relation to high and low levels of testosterone in serum during the breeding season. Forty-eight sperm samples from 30 sexually mature male brown bears (Ursus arctos) were obtained by electroejaculation, and their serum testosterone levels were assessed to sort the animals into 2 groups (high and low testosterone levels, threshold 5 ng/dl). The biochemical and protein compositions of the SP samples were assessed, and sperm motility was analyzed. We found that lactate dehydrogenase was significantly higher in the low-serum-testosterone samples, while concentrations of lipase and Mg+ values were significantly higher in the high-serum-testosterone samples. In contrast, sperm motility did not significantly differ (P>0.05) between the testosterone level groups (total motility: 74.42.8% in the high-level group vs. 77.1±4.7% in the low-level group). A reference digital model was constructed since there is no information for this wild species. To do this, all gel images were added in a binary multidimensional image and thirty-three spots were identified as the most-repeated spots. An analysis of these proteins was done by qualitative equivalency (isoelectric point and molecular weight) with published data for a bull. SP protein composition was compared between bears with high and low serum testosterone, and three proteins (binder of sperm and two enzymes not identified in the reference bull) showed significant (P<0.05) quantitative differences. We conclude that male bears with high or low serum testosterone levels differs only in some properties of their SP, differences in enzyme LDIP2, energy source LACT2, one protein (similar to BSP1) and Mg ion were identified between these two groups. These data may inform the application of SP to improve bear semen extenders.

Semen characteristics, extension, and cryopreservation of Rusa deer (Rusa timorensis)

AIM

The objective of this research is to report parameters for breeding soundness evaluation, semen extension, and cryopreservation in Rusa timorensis.

MATERIALS AND METHODS

Seven healthy stags were chosen for semen collection using an electroejaculator. The collections were performed twice in a breeding season between February and June 2016. Samples were collected between 2 and 3 weeks interval, collected twice for each animal. Semen was evaluated, extended, and cryopreserved using four different extenders; Andromed^®, BioXcell^®, Triladyl^®, and a modified Tris-egg yolk combined with Eurycoma longifolia Jack.

RESULTS

R. timorensis semen characteristics according to volume (ml), color, sperm concentration (10⁶/ml), general motility (%), progressive motility (%), and % morphology of normal spermatozoa are 0.86±0.18 ml, thin milky to milky, 1194.2±346.1 10⁶/ml, 82.9±2.8%, 76.1±4.8%, and 83.9±4.8%, respectively.

CONCLUSION

Semen characteristics of R. timorensis collected by electroejaculation is good allowing for cryopreservation and future artificial insemination work. The most suitable extender for Rusa deer semen is Andromed^®.

Proteomic Investigation of Ram Spermatozoa and the Proteins Conferred by Seminal Plasma

Sperm proteomes have emerged for several species; however, the extent of species similarity is unknown. Sheep are an important agricultural species for which a comprehensive sperm proteome has not been produced. In addition, potential proteomic factors from seminal plasma that may contribute to improved fertility after cervical insemination are yet to be explored. Here we use liquid chromatography-tandem mass spectrometry to investigate the proteome of ejaculated ram spermatozoa, with quantitative comparison to epididymal spermatozoa. We also present a comparison to published proteomes of five other species. We identified 685 proteins in ejaculated ram spermatozoa, with the most abundant proteins involved in metabolic pathways. Only 5% of ram sperm proteins were not detected in other species, which suggest highly conserved structures and pathways. Of the proteins present in both epididymal and ejaculated ram spermatozoa, 7% were more abundant in ejaculated spermatozoa. Only two membrane-bound proteins were detected solely in ejaculated sperm lysates: liver enriched gene 1 (LEG1/C6orf58) and epidermal growth factor-like repeats and discoidin I-like domains 3 (EDIL3). This is the first evidence that despite its relatively complex proteomic composition, seminal plasma exposure leads to few novel proteins binding tightly to the ram sperm plasma membrane.