High total antioxidant capacity of the porcine seminal plasma (SP-TAC) relates to sperm survival and fertility

Cobalt's role in modulating antioxidant systems and semen quality in males

The present study investigated associations between environmental exposure to cobalt (Co) and the levels of oxidative stress parameters and the antioxidant defense system in the seminal plasma of fertile males. The study population consisted of 117 healthy, non-smoking, fertile men from the southern region of Poland. The study was carried out in 2021-22. Based on the median cobalt levels in seminal plasma, subjects were divided into two groups: those with low (Co-L) and high (Co-H) cobalt concentrations. Semen parameters assessed according to WHO 2021 recommendations. After the analysis of spermiograms, observed reduction in progressive motility after 1 h was found in the Co-H group. Moreover, superoxide dismutase (SOD), glutathione S-transferase (GST) in the Co-H group had lower activity and GR higher activity. The OSI (Oxidative stress index) were higher in the group with high cobalt concentration in semen. The concentrations of redox balance parameters: TOS, TAC and OSI significantly were higher in the Co-high group as well as GR activity. Environmental exposure to cobalt decreases sperm motility in both normal and abnormal semen. The findings from this study affirm that cobalt can induce oxidative stress and alter oxidative stress markers in semen.

Chromatin condensation but not DNA integrity of pig sperm is greater in the sperm-rich fraction

BACKGROUND

Protamination and condensation of sperm chromatin as well as DNA integrity play an essential role during fertilization and embryo development. In some mammals, like pigs, ejaculates are emitted in three separate fractions: pre-sperm, sperm-rich (SRF) and post sperm-rich (PSRF). These fractions are known to vary in volume, sperm concentration and quality, as well as in the origin and composition of seminal plasma (SP), with differences being also observed within the SRF one. Yet, whether disparities in the DNA integrity and chromatin condensation and protamination of their sperm exist has not been interrogated.

RESULTS

This study determined chromatin protamination (Chromomycin A3 test, CMA3), condensation (Dibromobimane test, DBB), and DNA integrity (Comet assay) in the pig sperm contained in the first 10 mL of the SRF (SRF-P1), the remaining portion of the sperm-rich fraction (SRF-P2), and the post sperm-rich fraction (PSRF). While chromatin protamination was found to be similar between the different ejaculate fractions (P > 0.05), chromatin condensation was seen to be greater in SRF-P1 and SRF-P2 than in the PSRF (P = 0.018 and P = 0.004, respectively). Regarding DNA integrity, no differences between fractions were observed (P > 0.05). As the SRF-P1 has the highest sperm concentration and ejaculate fractions are known to differ in antioxidant composition, the oxidative stress index (OSi) in SP, calculated as total oxidant activity divided by total antioxidant capacity, was tested and confirmed to be higher in the SRF-P1 than in SRF-P2 and PSRF (0.42 ± 0.06 vs. 0.23 ± 0.09 and 0.08 ± 0.00, respectively; P < 0.01); this index, in addition, was observed to be correlated to the sperm concentration of each fraction (Rs = 0.973; P < 0.001).

CONCLUSION

While sperm DNA integrity was not found to differ between ejaculate fractions, SRF-P1 and SRF-P2 were observed to exhibit greater chromatin condensation than the PSRF. This could be related to the OSi of each fraction.

Progress on the roles of zinc in sperm cryopreservation

One of the effective methods for the long-term preservation of mammalian genetic resources is the cryopreservation of semen. However, a number of parameters, including diluents, the rate of freezing and thawing, cryoprotectants, etc., can easily alter the survival of frozen-thawed sperm. Numerous studies have documented the addition of a variety of zinc compounds, to the diluents used to cryopreserve sperm. The primary objective of this review is to briefly describe that adding zinc to diluents as an antioxidant significantly enhances frozen-thawed sperm quality. Second, a summary of the present understanding of zinc's molecular mechanism on semen cryopreservation is provided. Thirdly, this study addresses that nanoparticles of zinc can offer suggestions for raising cryopreservation effectiveness.

Relationship between biochemical parameters and paraoxonase 1 activity of boar seminal plasma and semen quality

The aim of this study was to examine the biochemical components and the parameters of antioxidant protection in the seminal plasma (SP) of boars, as well as their relationship with semen quality parameters. Thirty-six boars were included in the study, whose ejaculates were divided into two groups: Group I (good quality semen, > 70% progressively motile sperm, < 20% spermatozoa with abnormal morphology, n = 16), and Group II (poor quality semen, < 70% progressively motile sperm, > 20% spermatozoa with abnormal morphology, n = 20). Significantly higher concentrations of ionized calcium (iCa), total cholesterol (TC), lactate-dehydrogenase (LDH) activity, as well as significantly higher values ​​of antioxidant protection parameters: thiol groups (-SH), paraoxonase 1 (PON1), and total antioxidant capacity (TAC) ) were found in the good quality semen, while higher phosphorus (P) concentrations and increased alkaline-phosphatase (ALP) activity were found in the semen of poor quality. A negative correlation of total and progressive sperm motility with P and ALP was found in all examined semen samples, while a positive correlation was found with PON1 and TAC. The percentage of fast sperm cells positively correlated with iCa, chlorine (Cl), lactate, LDH and TAC, while a negative correlation was found with P, magnesium (Mg) and the enzyme creatine-kinase (CK). The percentage of immobile sperm positively correlated with P and ALP, and negatively correlated with TC, CK, PON1 and TAC. Elevated values ​​of PON1 and TAC in SP and a positive correlation with sperm motility indicate the possible use of these parameters as sensitive biomarkers of boar semen quality. To the best of our knowledge there are no published data on association between PON1 activity and boar semen quality.

Selenium Nanoparticles as Potential Antioxidants to Improve Semen Quality in Boars

Selenium is an essential compound which can influence the fertility of boars by a greater margin. In past decades, research was mainly focused on a bioavailability of various selenium forms and the effect on semen quality. Recently, nanotechnology has expanded the possibilities of selenium supplementation research. Twenty-one Duroc boars (three groups with seven boars each) were included in this experiment with the first group being a control group with no selenium supplementation, and the second group being supplemented with 0.3 mg Se/kg of selenium in inorganic form of Na2SeO3. The third group was supplemented with selenium nanoparticles (100 nm) at the same dose as that of the second group. The experiment lasted for 126 days (three spermatogenesis cycles of boars) and the antioxidant parameters of boar semen were analysed at 42, 84 and 126 days, respectively. The antioxidant parameters (DPPH, FRAP, DMPD, GSH, GSSG) were not influenced by both Se2NO3 and selenium nanoparticle supplementation during this experiment. At the end of the monitored period, significantly higher (p < 0.004) antioxidant readings were observed by using the ABTS method but not the DPPH, DMPD and FRAP methods on the supplemented groups compared to the control. Moreover, selenium-nanoparticle-supplemented groups showed elevated glutathione peroxidase activity in the seminal fluid (p < 0.008). However, the selenium nanoparticle supplementation has not shown an improving effect on sperm quality. This could be considered as a safe alternative to inorganic selenium as well as having a potential to enhance the antioxidant properties of the semen of boars.

Antioxidants and Oxidants in Boar Spermatozoa and Their Surrounding Environment Are Associated with AMPK Activation during Liquid Storage

Activation of the AMP-activated protein kinase (AMPK) has been demonstrated to be beneficial for boar sperm quality and functionality, while the underlying mechanism of AMPK activation of boar spermatozoa remains obscure. This study aimed to explore the effect of antioxidants and oxidants in boar spermatozoa and their surrounding fluid (SF) on the activation of AMPK during the liquid storage. Ejaculates from Duroc boars, routinely used for semen production, were collected and diluted to a final concentration of 25 × 106/mL. In experiment 1, twenty-five semen samples from eighteen boars were stored at 17 °C for 7 days. In experiment 2, three pooled semen samples created from nine ejaculates of nine boars were used, and each sample was treated with 0, 0.1, 0.2, and 0.4 μM/L H2O2 and stored at 17 °C for 3 h. Sperm quality and functionality, antioxidants and oxidants in boar spermatozoa and SF, the intracellular AMP/ATP ratio, and the expression levels of the phosphorylated AMPK (Thr172) were determined. Sperm quality significantly decreased with storage time in terms of viability (p < 0.05). Antioxidant and oxidant levels were markedly affected with storage time, with a decline in the SF total antioxidant capacity (TAC) (p < 0.05), SF malondialdehyde (MDA) (p < 0.05), and the sperm’s total oxidant status (TOS), as well as a fluctuation in sperm superoxidase dismutase-like (SOD-like) activity (p < 0.05). The intracellular AMP/ATP ratio increased (p < 0.05) on day 4 and subsequently decreased to its lowest value on days 6 and 7 (p < 0.05). The phosphorylated AMPK levels increased from day 2 to day 7 (p < 0.05). Correlation analyses indicate that sperm quality during liquid storage was correlated to antioxidants and oxidants in spermatozoa and SF (p < 0.05), which were correlated to the phosphorylation of sperm AMPK (p < 0.05). Treatment with H2O2 induced damages in sperm quality (p < 0.05), a decline in antioxidant levels (SF TAC, p < 0.05; sperm SOD-like activity, p < 0.01), an increase in oxidant levels (SF MDA, p < 0.05; intracellular ROS production, p < 0.05), a higher AMP/ATP ratio (p < 0.05), and phosphorylated AMPK levels (p < 0.05) in comparison with the control. The results suggest that antioxidants and oxidants in boar spermatozoa and SF are involved in AMPK activation during liquid storage.

Effect of zinc on boar sperm liquid storage

Storage and transport of liquid boar sperm for artificial insemination (AI) requires the addition of solutions called extenders, which increase the volume of the ejaculate and help preserve its functional characteristics. Yet, the quality of sperm decreases over time primarily due to the increased production of reactive oxygen species (ROS) that damage the plasma membrane. Many commercial extenders are supplemented with additives that mitigate this effect. In semen, zinc is supplied at high concentration on the seminal plasma and helps protect the plasma membrane of sperm. However, zinc in the seminal plasma is diluted and chelated upon addition of extenders for storage, potentially reducing its antioxidant effect. Here we characterize viability, motility, mitochondrial activity, DNA integrity and ROS content of boar sperm diluted with Sus (Medi Nova, Italy) extender supplemented with different concentrations of ZnCl₂, at intervals after dilution during 3 days. The ability of sperm supplemented with 2 mM ZnCl₂ to fertilize oocytes in vivo of was also tested. Sperm viability was over 82% for all treatments. Mitochondrial integrity analysis, measured by Cytochrome c activity, indicated a protector effect of Zn, noted as a reduced number of sperm with extensive loss of mitochondrial activity. Acrosomal integrity was improved by treatment with all concentrations of ZnCl₂ tested. Sperm kinematics were affected by treatment with ZnCl₂, showing higher percentage of progressive and rapid sperm in doses supplemented with 2mM ZnCl₂. ROS levels and chromatin integrity did not show differences between ZnCl₂-supplemented doses and the control. Fertilization rate, total number, live, still born and mummified piglets did not change when sperm were diluted with extender containing 2 mM ZnCl₂. The presented characterization indicates that Zn addition to Sus extender have a protective effect on mitochondrial sheath and acrosomal membranes; and provides the basis for further studies aimed to optimize sperm performance in AI.

Linseed oil in boar's diet improved in vivo fertility and antioxidant status

The reactive oxygen species (ROS) which are produced during storage of boar semen are causing oxidative stress and leads to poor fertility. Also, tropical and sub-tropical weather condition adversely impacts the physicomorphological quality and fertility of boar sperm. The aim of this study was to examine the effects of feeding linseed oil to boar on its seminal attributes, sperm kinetics, biomarkers of antioxidant, fatty acid profile of seminal plasma (SP) and sperm and in vivo fertility. Six Hampshire crossbreed boars were fed with 90 ml linseed oil (LIN) whereas six Hampshire crossbreed boars were fed 90 ml canola oil (CON) for 16 weeks. Sperm quality was evaluated (60 ejaculates for each group; a total of 120 ejaculates) for motility, livability, abnormal morphology, acrosomal membrane integrity, hypo-osmotic swelling test (HOST) and sperm kinetic parameters by computer assisted semen analysis (CASA) at 0 h and at 72 h of storage at 17°C. Biomarkers of antioxidant (glutathione peroxidase; GPx, catalase; CAT, total antioxidant capacity; TAC) and malondialdehyde (MDA) were measured in SP and serum. Gas chromatography-mass spectrometry (GC-MS) was used for the estimation of fatty acid composition of SP and sperm. Boars fed with linseed oil had higher semen volume (p < .01) and more total sperm numbers (p < .01). Feeding linseed oil to boar enhanced seminal attributes (p < .05) at 0 h as well as at 72 h of storage. Linseed oil feeding (p < .01) improved biomarkers of antioxidants and significantly (p < .01) lowered the lipid peroxidation in serum and SP. Linseed oil feeding (p < .05) increased the proportion of alpha linolenic (ALA), arachidonic and docosahexaenoic (DHA) fatty acids in SP. The ratio of n-6 to n-3 fatty acids in sperm increased significantly (p < .01) in treatment group. Farrowing rate was significantly (p < .05) higher in treatment group. In conclusion, feeding linseed oil to boar improved the in vivo fertility, enhanced antioxidant capacity and increased the DHA content of SP and sperm.

Contributions of seminal plasma proteins to fertilizing ability of bull sperm: A meta-analytical review

Seminal plasma is a dynamic, intricate combination of fluids from the testicles, epididymides, seminal vesicles, bulbourethral glands, and prostate, containing molecules that modulate sperm functions, post-fertilization events, and the female reproductive tract physiology. Significant variations in sperm parameters and fertility status of bulls relate to differences in the seminal plasma proteome. In this framework, a meta-analytical study was conducted examining 29 studies (published between 1990 and 2021) to ascertain the effects of seminal fluid proteins on parameters associated with bull fertility and the influence of distinct methodologies on such effects. Our results revealed that seminal proteins ameliorate sperm parameters, such as motility, integrity, capacitation, and fertilizing ability, and favours sperm protection. Seminal binder of sperm proteins and beta-defensin 126 highly favoured sperm protection when cells were collected from the epididymis by retrograde flux and analysed under room temperature conditions. Furthermore, seminal proteins improved the motility and quality of Bos taurus sperm collected by artificial vagina, mainly in the presence of heparin-binding proteins. The key limitations faced by this meta-analysis were the paucity of studies evaluating the effects of whole seminal fluid proteins and the limited number of studies conducted in vivo. In conclusion, the present meta-analytical study confirms that seminal proteins improve fertility-related parameters in the bovine species. However, methodological strategies used by authors are diverse, with distinct endpoints and methods. Thus, the translational aspects of seminal plasma research should be taken into consideration to precisely define how seminal proteins can be harnessed to advance reproductive biotechnology.

Determination of double- and single-stranded DNA breaks in bovine sperm is predictive of their fertilizing capacity

BACKGROUND

The analysis of chromatin integrity has become an important determinant of sperm quality. In frozen-thawed bovine sperm, neither the sequence of post-thaw injury events nor the dynamics of different types of sperm DNA breaks are well understood. The aim of the present work was to describe such sperm degradation aftermath focusing on DNA damage dynamics, and to assess if this parameter can predict pregnancy rates in cattle.

RESULTS

A total of 75 cryopreserved ejaculates from 25 Holstein bulls were evaluated at two post-thawing periods (0-2 h and 2-4 h), analyzing global and double-stranded DNA damage through alkaline and neutral Comet assays, chromatin deprotamination and decondensation, sperm motility, viability, acrosomal status, and intracellular levels of total ROS, superoxides and calcium. Insemination of 59,605 females was conducted using sperm from the same bulls, thus obtaining the non-return to estrus rates after 90 d (NRR). Results showed an increased rate of double-stranded breaks in the first period (0-2 h: 1.29 ± 1.01%/h vs. 2-4 h: 0.13 ± 1.37%/h; P <  0.01), whereas the rate of sperm with moderate + high single-stranded breaks was higher in the second period (0-2 h: 3.52 ± 7.77 %/h vs. 2-4h: 21.06 ± 11.69 %/h; P < 0.0001). Regarding sperm physiology, viability decrease rate was different between the two periods (0-2 h: - 4.49 ± 1.79%/h vs. 2-4 h: - 2.50 ± 3.39%/h; P = 0.032), but the progressive motility decrease rate was constant throughout post-thawing incubation (0-2 h: - 4.70 ± 3.42%/h vs. 2-4 h: - 1.89 ± 2.97%/h; P > 0.05). Finally, whereas no correlations between bull fertility and any dynamic parameter were found, there were correlations between the NRR and the basal percentage of highly-damaged sperm assessed with the alkaline Comet (Rs = - 0.563, P = 0.003), between NRR and basal progressive motility (Rs = 0.511, P = 0.009), and between NRR and sperm with high ROS at 4 h post-thaw (Rs = 0.564, P = 0.003).

CONCLUSION

The statistically significant correlations found between intracellular ROS, sperm viability, sperm motility, DNA damage and chromatin deprotamination suggested a sequence of events all driven by oxidative stress, where viability and motility would be affected first and sperm chromatin would be altered at a later stage, thus suggesting that bovine sperm should be used for fertilization within 2 h post-thaw. Fertility correlations supported that the assessment of global DNA damage through the Comet assay may help predict bull fertility.

Extracellular vesicles in seminal plasma: A safe and relevant tool to improve fertility in livestock?

Seminal plasma (SP) is not a pre-requisite for pregnancy. Yet, this heterogeneous, composite SP has proven relevant for fertility, as mediator for cell-to-cell communication between producing cells, spermatozoa and the female internal genital tract, regulating complex reproductive processes. Bearing hormones, proteins, cytokines as well as nuclei acids in nano-sized lipid bilayer seminal extracellular vesicles (sEVs), the SP concerts signaling to the female. Signals influence timing of ovulation, sperm transport and, particularly, enable the female immune system to balance her cryptic choice to engage into pregnancy or reject an eventual fertilization. This essay, focusing on livestock in general and pigs in particular, discusses the intrinsic roles of sEVs with regards to reproductive homeostasis, while binding and internalizing their cargo in spermatozoa and female tract epithelia to regulate their functional activity. Since prior studies had inconclusive results using bulk SP or single SP-contained free molecules, argumentation is hereby provided to increase the current incipient research on livestock sEVs, where fragile molecules relevant for fertility are shielded from degradation during handling. Seminal EVs isolated from SP can be used for andrological diagnosis and perhaps to select breeders with optimal fertility. Moreover, sEVs can be laboratory-uploaded with specific molecules or even engineered as lipid nanodroplets used as additives for extenders to improve fertility after artificial insemination (AI) or reproductive biotechnologies.

Study on cryopreservation of Guanzhong dairy goat semen with bovine semen seminal plasma

There are phospholipase and yolk agglutinase in the seminal plasma of dairy goat. The existence of these enzymes will hydrolyze lecithin in yolk into lysophosphatides and cause the change of pH value of diluent, resulting in toxic and side effects on sperm. In order to explore the effect of bovine seminal plasma replacing different doses of dairy goat seminal plasma (0%, 25%, 50%, 100%) on semen freezing quality of Guanzhong dairy goat, we used computer-aided sperm analysis (CASA) system, specific fluorescent probe detection technology, hypo osmotic swelling test (HOST), oxidation index determination and in vivo fertilization verification test to study the semen cryopreservation of Guanzhong dairy goat. The results showed that if we used bovine seminal plasma instead of 100% dairy goat seminal plasma, the sperm motility, plasma membrane functionality and acrosome integrity rate were the highest after thawing, reaching 67.04%, 38.12% and 68.83% respectively, which was significantly higher than that of other groups (P < 0.05); In terms of oxidation indexes, the values of SOD and GSH-PX in sperm of dairy goats were 199.78 U/mL and 133.55 U/L, respectively, which were significantly higher than those in other groups (P < 0.05), and the values of ROS and MDA were 397.58 U/mL and 5.16 nmol/L, respectively, which were significantly lower than those in other groups (P < 0.05); The results of artificial insemination also showed that using bovine seminal plasma instead of 100% of dairy goat seminal plasma could significantly improve the fertilization ability of sperm. The quality of frozen Guanzhong dairy goat sperm can be improved by using bovine seminal plasma instead of dairy goat seminal plasma and using bovine diluent.

Effect of Glutathione on Sperm Quality in Guanzhong Dairy Goat Sperm During Cryopreservation

In the process of cryopreservation of dairy goat semen, it will face many threats such as oxidative damage, which will affect the motility and plasma membrane function of sperm. As an endogenous antioxidant in animals, glutathione (GSH) can significantly improve the quality of thawed sperm when added to the frozen diluent of semen of pigs and cattle. In this study, different concentration gradients of GSH [0 mmol/L (control), 1, 2, 3, 4 mmol/L] were added to the frozen diluent of Guanzhong dairy goat semen. By detecting the sperm motility parameters, acrosome intact rate and plasma membrane intact rate after thawing, the effect of GSH on the cryopreservation of dairy goat semen was explored. Sperm motility parameters were measured with the computer-aided sperm analysis (CASA) system (total power, TM; forward power, PM; linearity, LIN; average path speed, VAP; straight line speed, VSL; curve speed, VCL; beat cross frequency, BCF). The sperm acrosome integrity rate after thawing was detected by a specific fluorescent probe (isothiocyanate-labeled peanut agglutinin, FITC-PNA), and the sperm plasma membrane integrity rate after thawing was detected by the hypotonic sperm swelling (HOST) method. Reactive oxygen species (ROS) kit, malondialdehyde (MDA) kit, superoxide dismutase (SOD) kit, glutathione peroxidase (GSH-PX) kit were used to detect various antioxidant indicators of thawed sperm. in vitro fertilization experiment was used to verify the effect of adding glutathione on sperm fertilization and embryo development. The results showed that when the concentration of glutathione was 2 mmol/l, the sperm viability, plasma membrane intact rate, and acrosome intact rate were the highest after thawing, reaching 62.14, 37.62, and 70.87% respectively, and they were all significantly higher. In terms of antioxidant indexes; the values of SOD and GSH-PX were 212.60 U/ml and 125.04 U/L, respectively, which were significantly higher than those of the control group; The values of ROS and MDA were 363.05 U/ml and 7.02 nmol/L, respectively, which were significantly lower than the control group. The addition of 2 mmol/L glutathione significantly improves the fertilization ability of sperm. In short, adding 2 mmol/l glutathione to the semen diluent can improve the quality of frozen Guanzhong dairy goat sperm.

Relevance of the Ejaculate Fraction and Dilution Method on Boar Sperm Quality during Processing and Conservation of Seminal Doses

During boar semen processing and distribution, maximizing the work protocols in the laboratories becomes essential for the conservation of seminal doses. One of the recent implementations in the boar studs to improve efficiency has been semi-automatic semen collection systems, which do not allow to discard fractions of the ejaculate. The objective of this work was to evaluate the dilution method and vibrations (simulating delivery transport) effect on sperm quality (motility, viability, morphology, thermo-resistance test) according to the fraction of ejaculate collected. Two different fractions of the ejaculate were obtained [rich fraction (RF); total fractions (TF)] from six boars, and two dilution methods applied [pouring the extender over the semen (control; ES); pouring the semen over the extender (reverse; SE)]. The seminal doses (2000 × 10⁶ sperm/50 mL) were preserved for 5 days. The results showed that the fraction collected affects sperm quality (better total and progressive motility, and faster sperm in TF; p < 0.05) regardless of the dilution method applied. However, these differences diminished after submitting the semen to the thermo-resistance test, with only differences in sperm viability being observed (p < 0.05). When seminal doses were subjected to vibrations, the sperm viability was more affected in the TF than in the RF group (p < 0.05). In conclusion, using the TF ejaculate leads to comparable results to the RF in sperm quality during storage regardless of the dilution method applied. However, the vibrations of seminal doses are more affected in doses prepared with TF than with RF, although more factors should be included to approach the real conditions during transport.

The TUNEL assay underestimates the incidence of DNA damage in pig sperm due to chromatin condensation

Inconsistencies in the relationship between sperm DNA fragmentation and reproductive outcomes as well as the low incidence in farm animals raise concerns on its actual value as a sperm quality parameter. Previous studies suggested that the different sensitivity of techniques evaluating DNA fragmentation could explain variations in the correlation with reproductive outcomes. While the TUNEL assay is one of the most standardized methods to detect DNA damage and cell death, the steric impediment for the terminal nucleotidyl transferase enzyme to access the highly condensed sperm nucleus may decrease the ability of this test to detect internal DNA breaks. In the present study, we sought to determine whether increasing chromatin decondensation makes the TUNEL assay more sensitive to detect DNA damage in pig sperm. We compared three chromatin decondensation treatments (2 mM DTT for 45 min; 5 mM DTT for 8 min and further 45 min; and 5 mM DTT+ 1 M NaCl for 8 min) through the Chromomycin A3 test (CMA3). While incubation with DTT increased the percentages of sperm with decondensed chromatin, regardless of concentration and time of incubation (P < 0.05), the extent of that decondensation was higher when 5 mM DTT was combined with 1 M NaCl. In addition, the TUNEL assay detected a higher number of DNA breaks in sperm with decondensed chromatin (1.89% ± 1.63% vs 8.74% ± 6.05%; P = 0.003). This study shows, for the first time, that previous chromatin decondensation increases the sensitivity of the TUNEL assay to detect DNA damage in pig sperm. These findings also support that larger chromatin decondensation is needed in order for DNA damage to be evaluated properly in species containing protamine P1 only.

Measurement of Oxidative Stress Index in Seminal Plasma Can Predict In Vivo Fertility of Liquid-Stored Porcine Artificial Insemination Semen Doses

The study evaluated the relation between the oxidative stress index (OSI) in porcine seminal plasma (n = 76) with sperm resilience and in vivo fertility (farrowing rate and litter size of 3137 inseminated sows) of liquid-stored artificial insemination (AI) semen doses. The OSI was assessed as the ratio of advanced oxidation protein products to Trolox-equivalent antioxidant capacity, both measured using an automated analyzer. Sperm motility (computer-assisted sperm analyzer) and viability (flow cytometry) were evaluated in semen AI-doses at 0 and 72 h of storage at 17 °C. Sperm resilience was defined as the difference between storage intervals. Semen AI-doses were hierarchically clustered as having high, medium and low seminal OSI (p < 0.001) with those of low displaying higher resilience (p < 0.01). Boars were hierarchically clustered into two groups (p < 0.001) as having either positive or negative farrowing rate and litter size deviation; the negative one showing higher seminal OSI (p < 0.05). In sum, seminal OSI was negatively related to sperm motility and the in vivo fertility of liquid-stored boar semen AI-doses, with the receiver operating characteristic curve presenting seminal OSI as a good predictive biomarker of in vivo fertility of AI-boars (area under the curve: 0.815, p < 0.05).

Impact of Oxidative Stress on Male Reproduction in Domestic and Wild Animals

Oxidative stress occurs when the levels of reactive oxygen species (ROS) overcome the antioxidant defenses of the organism, jeopardizing several biological functions, including reproduction. In the male reproductive system, oxidative stress not only impairs sperm fertility but also compromises offspring health and survival, inducing oxidative damage to lipids, proteins and nucleic acids. Although a clear link between oxidative stress and male fertility disorders has been demonstrated in humans and laboratory rodents, little information is available about the implications of impaired redox homeostasis in the male fertility of domestic and wild animals. Therefore, this review aims to provide an update regarding the intrinsic and extrinsic factors that are associated with oxidative stress in the male reproductive system and their impact on the reproductive performance of domestic and wild animals. The most recent strategies for palliating the detrimental effects of oxidative stress on male fertility are reviewed together with their potential economic and ecological implications in the livestock industry and biodiversity conservation.

Role of Antioxidants in Cooled Liquid Storage of Mammal Spermatozoa

Cooled preservation of semen is usually associated with artificial insemination and genetic improvement programs in livestock species. Several studies have reported an increase in reactive oxidative species and a decrease in antioxidant substances and sperm quality parameters during long-term semen storage at refrigerated temperatures. The supplementation of antioxidants in extenders before refrigeration could reduce this detrimental effect. Various antioxidants have been tested, both enzymatic, such as superoxide dismutase and catalase, and non-enzymatic, such as reduced glutathione, vitamins E and C and melatonin. However, the problem of oxidative stress in semen storage has not been fully resolved. The effects of antioxidants for semen-cooled storage have not been reviewed in depth. Therefore, the objective of the present study was to review the efficiency of the supplementation of antioxidants in the extender during cooled storage of semen in livestock species.

Aldose Reductase B1 in Pig Seminal Plasma: Identification, Localization in Reproductive Tissues, and Relationship With Quality and Sperm Preservation

Aldose reductase B1 (AKR1B1), a NADPH-dependent enzyme that belongs to the aldo-keto reductase protein superfamily, has been reported to be involved in both male and female reproductive physiology. The objectives of this study were: (1) to evaluate the concentration of SP-AKR1B1 in pig ejaculate fractions; (2) to describe the immunohistochemical localization of AKR1B1 alongside the boar genital tract; (3) to evaluate the relationship between SP-AKR1B1 and sperm quality/functionality parameters. Ejaculates from seven boars (one ejaculate per boar) were collected in separate portions [the first 10 mL of the sperm rich fraction (SRF-P1), the rest of the SRF (SRF-P2), and the post-SRF (PSRF)], and the concentration of SP-AKR1B1 was assessed using an enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry and immunoblotting targeting was conducted in the reproductive tissues of these boars. Additionally, the entire ejaculates of 14 boars (one ejaculate per boar) were collected and split into three separate aliquots for: (i) SP-AKR1B1 quantification; (ii) assessment of sperm concentration and morphology; and (iii) evaluation of sperm quality and functionality parameters upon ejaculate collection (0 h) and after 72 h of liquid storage at 17°C. Concentration of AKR1B1 in the SP of SRF-P1 (458.2 ± 116.33 ng/mL) was lower (P < 0.05) than that of SRF-P2 (1105.0 ± 229.80 ng/mL) and PSRF (1342.4 ± 260.18 ng/mL). Monomeric and dimeric AKR1B1 forms were expressed alongside the reproductive tissues, except in the bulbourethral glands. No relationship between SP-AKR1B1 and sperm quality/functionality parameters was observed either at 0 h or after 72 h of storage at 17°C. In conclusion, AKR1B1 is expressed in the reproductive organs of boars (except bulbourethral glands) and a higher concentration is found in the PSRF suggesting that seminal vesicles would be the main secretory source. However, this enzyme does not appear to be related to sperm quality/functionality or to the sperm ability to withstand liquid storage at 17°C.

Metabolite Profiling of Pig Seminal Plasma Identifies Potential Biomarkers for Sperm Resilience to Liquid Preservation

Metabolomic approaches allow the study of downstream gene expression events since metabolites are considered as the products of cell signaling pathways. For this reason, many studies in humans have already been conducted to determine the influence of the metabolites present in seminal plasma (SP) on sperm physiology, and to identify putative biomarkers. However, in livestock species, these relationships are yet to be uncovered. Thus, the present study aimed to explore: (i) if concentrations of metabolites in pig SP are related to sperm quality and functionality, and (ii) if they could predict the sperm resilience to liquid storage at 17°C. To this end, 28 ejaculates were individually collected and split into three aliquots: one was used for SP analysis through nuclear magnetic resonance (NMR) spectroscopy; another served for the evaluation of sperm concentration and morphology; and the last one was utilized to determine sperm functionality parameters using computer-assisted sperm analysis (CASA) and flow cytometry after 0 h and 72 h of liquid-storage at 17°C. NMR analysis allowed the identification and quantification of 23 metabolites present in pig SP which, except for fumarate, were not observed to follow a breed-dependent behavior. Moreover, specific relationships between metabolites and sperm variables were identified: (i) glutamate, methanol, trimethylamine N-oxide, carnitine, and isoleucine were seen to be related to some sperm quality and functionality parameters evaluated immediately after semen collection; (ii) leucine, hypotaurine, carnitine and isoleucine were found to be associated to the sperm ability to withstand liquid storage; and (iii) Bayesian multiple regression models allowed the identification of metabolite patterns for specific sperm parameters at both 0 h and 72 h. The identification of these relationships opens up the possibility of further investigating these metabolites as potential sperm functional biomarkers.

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.

Advancing Semen Evaluation Using Lipidomics

Developing a deeper understanding of biological components of sperm is essential to improving cryopreservation techniques and reproductive technologies. To fully ascertain the functional determinants of fertility, lipidomic methods have come to the forefront. Lipidomics is the study of the lipid profile (lipidome) within a cell, tissue, or organism and provides a quantitative analysis of the lipid content in that sample. Sperm cells are composed of various lipids, each with their unique contribution to the overall function of the cell. Lipidomics has already been used to find new and exciting information regarding the fatty acid content of sperm cells from different species. While the applications of lipidomics are rapidly evolving, gaps in the knowledge base remain unresolved. Current limitations of lipidomics studies include the number of available samples to analyze and the total amount of cells within those samples needed to detect changes in the lipid profiles across different subjects. The information obtained through lipidomics research is essential to systems and cellular biology. This review provides a concise analysis of the most recent developments in lipidomic research. This scientific resource is important because these developments can be used to not only combat the reproductive challenges faced when using cryopreserved semen and artificial reproductive technologies in livestock such as cattle, but also other mammals, such as humans or endangered species.

The role of endogenous antioxidants in male animal fertility

Mammalian semen is a physiological fluid composed of a cellular fraction (spermatozoa), and a liquid fraction (seminal plasma). Once delivered to the female genital tract, spermatozoa should be able to capacitate; a process which involves a plethora of biochemical and physiological changes required to fertilize the oocyte. Sperm production (spermatogenesis) occurs in the testes, whereby pluripotent spermatogonia differentiate to form the most morphologically specialized cells in the body. Further maturation of spermatozoa occurs in the epididymis, where they are stored prior to ejaculation. During this whole process, spermatozoa are exposed to different environments and cellular processes which may expose them to substantial levels of oxidative stress. To avoid damage associated with the unchecked production of reactive oxygen species (ROS), both spermatozoa, and the parts of the male genital tract in which they reside, are furnished with a suite of antioxidant molecules which are able to provide protection to these cells, thereby increasing their chance of being able to fertilize the oocyte and deliver an intact paternal genome to the future offspring. However, there are a host of reasons why these antioxidant systems may fail, including nutritional deficiencies, genetics, and disease states, and in these situations, a reduction or abolition of fertilizing capacity may result. This review paper focuses on the endogenous antioxidant defences available to spermatozoa during spermatogenesis and sperm maturation, the site of their production and their physiological role. Furthermore, we revised the causes and effects of antioxidant deficiencies (congenital or acquired during the animal's adulthood) on reproductive function in different animal species.

Oxidative and nitrosative stress in frozen-thawed pig spermatozoa. I: Protective effect of melatonin and butylhydroxytoluene on sperm function

The addition of antioxidants to the cryopreservation medium has been shown to exert a positive effect on the quality of frozen-thawed sperm in different species. The objective of the present study was to evaluate the effects of supplementing the freezing medium with butylhydroxytoluene (BHT) and melatonin (MEL) in frozen-thawed pig spermatozoa. With this purpose, six ejaculates coming from six separate boars were cryopreserved in traditional freezing medium (i.e. lactose/egg-yolk/glycerol; Control) supplemented with 1.0 mM BHT (BHT-1), 2.0 mM BHT (BHT-2), 0.01 μM MEL (MEL-1) and 1.0 μM MEL (MEL-2). We evaluated sperm viability, membrane lipid disorder, acrosome integrity, mitochondrial membrane potential, lipid peroxidation, oxidation of thiol groups, and levels of total reactive oxygen species (ROS), peroxynitrite and superoxide anion (·O₂^-). We also analysed total (TM) and progressive sperm motilities (PM), and kinetic parameters at post-thaw (T0, T30 and T60). The BHT-2 and MEL-2 groups presented higher viability and acrosome integrity, and lower levels of peroxynitrite, ·O₂^- and lipid peroxidation than the control (P < 0.05), whereas MEL-2 diminished the levels of total ROS (P < 0.05). TM and PM were not affected by the treatment, while, LIN and STR shows differences between experimental groups. In conclusion, the addition of BHT and MEL to cryopreservation medium diminishes oxidative and nitrosative stress markers, which has repercussions for the integrity of plasma and acrosomal membranes of frozen-thawed spermatozoa.

Butaphosphan and Cyanocobalamin Supplementation in Semen Extender on Chilled Boar Sperm Quality and Life Span

The objective of the present study was to determine the effect of butaphosphan and cyanocobalamin supplementation in semen extender on chilled boar sperm quality and life span. A total of 35 ejaculates of boar semen were included. The semen was diluted with Beltsville thawing solution extender supplemented with different concentrations of butaphosphan and cyanocobalamin [0 (control), 0.1, 0.2, 0.3, 0.4, and 0.5%] in the diluted semen. The semen samples were evaluated using a computer-assisted sperm analysis system to determine sperm motility and sperm kinetic parameters (i.e., the curvilinear velocity, VCL; straight line velocity, VSL; average path velocity, VAP; linearity, LIN; straightness, STR; amplitude of lateral head, ALH; wobble, WOB; and beat cross frequency, BCF). Additionally, sperm viability, acrosome integrity, mitochondrial activity, and plasma membrane integrity were evaluated after 4 (day 0), 72 (day 3), 120 (day 5), and 168 (day 7) h of storage using SYBR-14-ethidium homodimer-1 (EthD-1), EthD-1, JC-1, and the short hypo-osmotic swelling test, respectively. The analyses were carried out by using the general linear mixed model (MIXED) procedure of SAS. The statistical models for each data set included group, day after storage, and interaction between group and day after storage. The boar was included as a random effect. On day 0 after storage, progressive motility, VCL, VSL, VAP, and plasma membrane integrity of boar sperm in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the 0.4 and 0.5% groups (P < 0.05). On day 3 after storage, total motility and progressive motility, VCL, VSL, VAP, LIN, WOB, BCF, and plasma membrane integrity in 0.3% of butaphosphan and cyanocobalamin supplementation were significantly greater than those in the control group (P < 0.05). The total motility and progressive motility, VAP, and WOB in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the control group on day 5 after storage (P < 0.05). No effects of butaphosphan and cyanocobalamin supplementation on acrosome integrity and mitochondria activity were found on days 3, 5, and 7 after storage. However, the motility and progressive motility and the values for all sperm kinetic parameters except ALH in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the control group on day 7 after storage (P < 0.05). In conclusion, 0.3% of butaphosphan and cyanocobalamin supplementation in semen extender improved sperm motility, sperm activity, morphology, and life span in chilled boar sperm.

Antioxidants and their effect on the oxidative/nitrosative stress of frozen-thawed boar sperm

In swine, the use of frozen-thawed boar sperm for artificial insemination remains a suboptimal reproductive technology. Among the negative effects of cryopreservation on sperm cells, it is worth highlighting that cryopreservation causes irreversible alterations in motility and components of the sperm membrane as a result of dramatic changes in temperature (cooling/freezing curve) and osmolality. In addition, freeze-thawing may induce oxidative stress and increase the generation of reactive oxygen species (ROS) and nitrogen reactive species (RNS). While boar sperm cryopreservation has been reported to increase lipid peroxidation and the intracellular levels of hydrogen peroxide, less research on its impact on RNS has been conducted. Furthermore, previous studies have investigated the effects of supplementing cryopreservation media with antioxidants to counteract the deleterious effects of ROS and RNS. Antioxidants of synthetic origin or natural extracts have been used, with some showing noticeable and positive effects on functional sperm parameters both in vitro and in vivo. The aim of this review is to provide an update on the effect of different molecules with antioxidant capacity on the function of cryopreserved boar sperm.

Delays in processing and storage of pig seminal plasma alters levels of contained antioxidants

Seminal plasma (SP) antioxidants are considered biomarkers of sperm function and fertility for AI-boars. The current protocol for their measurement implies the SP was harvested immediately after ejaculation and prompt stored at -80 °C until analysis. Such protocol may be impractical for AI-centers. This study evaluated how SP levels of antioxidants were influenced by delays in (1) SP-harvesting (0 [control], 2 or 24 h at 17 °C after ejaculate collection), in (2) SP-freezing (0 [control] or 24 h at 17 °C after SP-harvesting) or (3) the temperature of storage (-80 °C [control] or - 20 °C). The SP-antioxidants evaluated were: glutathione peroxidase [GPx], superoxide dismutase [SOD], paraoxonase-1 [PON-1], trolox equivalent antioxidant capacity [TEAC] and oxidative stress index [OSI]. A total of 120 aliquots from 10 entire ejaculates were handled in three trials. They were centrifuged (1500 g, 10 min) for harvesting SP and antioxidants were measured with an Automatic Chemistry Analyzer. A 24 h-delay in harvesting the SP led to an increase (p˂0.001) in TEAC and SOD SP-levels, and a decrease (p˂0.05) of OSI and PON-1. Similarly, a 24 h-delay to freeze the SP increased (p˂0.01) TEAC values and decreased (p˂0.01) PON-1 and GPx activity levels. Finally, storing the SP at -20 °C decreased (p˂0.001) SP-levels of TEAC, PON-1 and GPx, and increased (p˂0.01) OSI values. Strong positive relationships (p˂0.001) were found between antioxidant SP-levels in processed samples and their respective controls. In sum, handling and SP storage influence antioxidant measurements in AI-boars. Reliable levels of SP-antioxidants can only be warranted if a strict protocol for harvesting and SP storage is followed.

Dietary flaxseed oil improve boar semen quality, antioxidant status and in-vivo fertility in humid sub-tropical region of North East India

Environmental stress in the form of high temperature humidity index (THI) in tropical and sub-tropical region negatively affects semen quality and fertility of boar. Therefore, the present study was done to evaluate the effect of supplementing flaxseed oil (FLO) to boar's diet on its semen quality, antioxidant status, fatty acid composition of seminal plasma and fertility under sub-tropical climate. For this purpose, six Hampshire crossbreed (50% Hampshire and 50% Gunghroo) boars were divided into two groups i.e control (CON) and treatment (FLO). In FLO and CON group, flaxseed and vegetable oil, respectively, was top dressed at the rate of 3% in basal diets for each boar on daily basis for 16 weeks during monsoon season. A total of 60 ejaculates, comprising 30 ejaculates from each group (ten ejaculates from each boar) were collected. Semen samples were evaluated for sperm quality parameters (SQPs: motility, viability, abnormality, acrosomal integrity and Hypo-osmotic swelling test) and velocity attributes by computer assisted semen analysis (CASA) at fresh and after 72 h of preservation at 17 °C. Antioxidant (glutathione peroxidase; GPx, catalase; CAT, total antioxidant capacity; TAC and malondialdehyde; MDA) were analyzed in seminal plasma and serum. Fatty acid compositions of seminal plasma were analyzed by gas chromatography-mass spectrometry (GC-MS). In-vivo fertility study was also conducted. Reaction time and false mounts were significantly (p < 0.05) reduced in FLO group as compared to CON group. Semen quality parameters were significantly (p < 0.05) improved at fresh stage and after 72 h of liquid storage in FLO group as compared to CON group. Velocity attributes (VAP, VSL, VCL, ALH, BCF and LIN) were significantly (p < 0.05) higher in FLO group. Flaxseed oil supplementation significantly (p < 0.01) enhanced serum GPx and CAT concentration. Serum and seminal plasma MDA concentration decreased significantly (p < 0.01) in FLO group. Similarly, GPx, TAC and CAT were significantly (p < 0.01) elevated in seminal plasma of FLO group. The study revealed that feeding of flaxseed oil altered the fatty acid composition of seminal plasma and significantly (p < 0.05) improved the farrowing rate. In summary, flaxseed oil supplementation improved the semen quality parameters and fertility of boars in sub-tropical climate by improving the antioxidant capacity and altering the fatty acid composition of seminal plasma.

Boar sperm incubation with reduced glutathione (GSH) differentially modulates protein tyrosine phosphorylation patterns and reorganization of calcium in sperm, in vitro fertilization, and embryo development depending on concentrations

The sperm in the female's reproductive tract undergo changes to fertilize the oocyte (sperm capacitation). These changes are regulated by redox system. However, some assisted reproductive technologies require sperm capacitation under in vitro conditions, though this increases the generation of ROS. Therefore, the aim of this study was to evaluate the effect of GSH as an antioxidant agent during the capacitation of boar sperm [evaluated by calcium compartmentalization, tyrosine phosphorylation (Tyr-P), motility, viability, and acrosomal integrity], in vitro fertilization (evaluated by penetration, monospermy, and efficiency %), and later embryo development (evaluated by cleavage and blastocyst rates, total number of cells per blastocyst and blastocyst diameter). Four experimental groups with different GSH concentrations (0-control, 0.5, 1, and 5 mM) were formed. When 1-GSH was added to the medium, the percentage of capacitated sperm increased after 4 h of incubation; the localization of Tyr-P was modified at 1 h and 4 h of incubation depending on the GSH concentration. Percentages of total and progressive sperm motility also increased at 4 h of incubation, but only in the 5-GSH group compared to control. Viability, acrosomal integrity, and general Tyr-P (Western blot) not differ among the experimental groups. The addition of GSH during gamete interaction increased penetration, monospermy, and efficiency rates in the 1-GSH group compared to the others. However, the effect of GSH was not observed in cleavage and blastocyst rates compared to the control. In conclusion, adding GSH modulates sperm capacitation (by means of calcium compartmentalization and tyrosine phosphorilation pattern) depending on its concentration, and improves IVF output at 1-GSH during gamete interaction.

Does the Act of Copulation per se, without Considering Seminal Deposition, Change the Expression of Genes in the Porcine Female Genital Tract?

Semen—through its specific sperm and seminal plasma (SP) constituents—induces changes of gene expression in the internal genital tract of pigs, particularly in the functional sperm reservoir at the utero-tubal junction (UTJ). Although seminal effects are similarly elicited by artificial insemination (AI), major changes in gene expression are registered after natural mating, a fact suggesting the act of copulation induces per se changes in genes that AI does not affect. The present study explored which pathways were solely influenced by copulation, affecting the differential expression of genes (DEGs) of the pre/peri-ovulatory genital tract (cervix, distal uterus, proximal uterus and UTJ) of estrus sows, 24 h after various procedures were performed to compare natural mating with AI of semen (control 1), sperm-free SP harvested from the sperm-peak fraction (control 2), sperm-free SP harvested from the whole ejaculate (control 3) or saline-extender BTS (control 4), using a microarray chip (GeneChip^® porcine gene 1.0 st array). Genes related to neuroendocrine responses (ADRA1, ADRA2, GABRB2, CACNB2), smooth muscle contractility (WNT7A), angiogenesis and vascular remodeling (poFUT1, NTN4) were, among others, overrepresented with distal and proximal uterine segments exhibiting the highest number of DEGs. The findings provide novel evidence that relevant transcriptomic changes in the porcine female reproductive tract occur in direct response to the specific act of copulation, being semen-independent.

1H Nuclear Magnetic Resonance of Pig Seminal Plasma Reveals Intra-Ejaculate Variation in Metabolites

In pigs, ejaculate is expelled in fractions, mainly the sperm-rich fraction (SRF) and the post-SRF (PSRF), which differ in both sperm content and origin. In addition, intra-ejaculate variability between fractions in terms of sperm reproductive characteristics has been previously reported, the highest sperm quality being observed in the first 10 mL of the SRF (SRF-P1). As seminal plasma (SP) composition has been purported to influence sperm physiology, the aim of this study was to profile pig SP metabolite composition and to find putative differences between the ejaculate portions (SRF-P1, the rest of SRF [SRF-P2], PSRF) and entire ejaculate (EE). To this end, ejaculates (n = 8, one per boar) were collected in fractions and SP was analyzed using 1H Nuclear Magnetic Resonance spectroscopy. We identified 19 metabolites present in all ejaculate portions and the EE, and reported correlations between the metabolites. Additionally, and for the first time in mammals, we found intra-ejaculate variability in the SP metabolites, observing different relative abundances in choline, glycerophosphocholine and glycine. Regarding their influence in sperm physiology, we hypothesize that these metabolites may explain the specific reproductive characteristics of each ejaculate portion. Finally, the reported SP metabolites could serve as a first steppingstone in the study of quality, functionality, and fertility biomarkers.

Divergent effect of fast- and slow-releasing H2S donors on boar spermatozoa under oxidative stress

Hydrogen sulphide (H₂S) is involved in the physiology and pathophysiology of different cell types, but little is known about its role in sperm cells. Because of its reducing properties, we hypothesise that H₂S protects spermatozoa against the deleterious effects of oxidative stress, a condition that is common to several male fertility disorders. This study aimed i) to determine the total antioxidant capacities of Na₂S and GYY4137, which are fast- and slow-releasing H₂S donors, respectively, and ii) to test whether H₂S donors are able to protect spermatozoa against oxidative stress. We found that Na₂S and GYY4137 show different antioxidant properties, with the total antioxidant capacity of Na₂S being mostly unstable and even undetectable at 150 µM. Moreover, both H₂S donors preserve sperm motility and reduce acrosome loss, although the effects were both dose and donor dependent. Within the range of concentrations tested (3–300 µM), GYY4137 showed positive effects on sperm motility, whereas Na₂S was beneficial at the lowest concentration but detrimental at the highest. Our findings show that Na₂S and GYY4137 have different antioxidant properties and suggest that both H₂S donors might be used as in vitro therapeutic agents against oxidative stress in sperm cells, although the optimal therapeutic range differs between the compounds.

Lyophilized seminal plasma can improve stallion semen freezability

The aim of this study was to evaluate the effect of lyophilized seminal plasma (LSP) on stallion semen freezability. Seminal plasma from 30 stallions was lyophilized to obtain a pool of LSP. Fifteen ejaculates from five stallions were supplemented before freezing with 0 mg/mL (Control), 1.44 mg/mL (LSP1), 5.04 mg/mL (LSP2) or 8.68 mg/ mL (LSP3) of LSP. Total antioxidant capacity (TAC) of LSP was assessed using Oxygen Radical Absorbance Capacity (ORAC) assay. Post-thaw motility and kinetics, sperm viability, normal morphology and membrane integrity were evaluated. Completely randomized mixed models were fitted for data analyses. The results was analyzed based on freezability of semen samples. TAC for LSP pool was 13679.4±911.6 μmol Trolox 100/g (ORAC units). Semen supplementation with LSP1 and LSP2 showed a positive effect on post-thaw total motility and membrane integrity. Supplementation with LSP3 showed a decrease in post-thaw total and progressive motility, straight line velocity and sperm viability. For poor freezability semen samples, supplementation with LSP1 and LSP2, showed higher post-thaw total motility and membrane integrity than good freezability semen samples. In conclusion, supplementation with LSP can improve the post-thaw seminal quality of stallion semen with poor freezability.

C60 Fullerenes Suppress Reactive Oxygen Species Toxicity Damage in Boar Sperm

We report the carboxylated C₆₀ improved the survival and quality of boar sperm during liquid storage at 4 °C and thus propose the use of carboxylated C₆₀ as a novel antioxidant semen extender supplement. Our results demonstrated that the sperm treated with 2 μg mL^-1 carboxylated C₆₀ had higher motility than the control group (58.6% and 35.4%, respectively; P ˂ 0.05). Moreover, after incubation with carboxylated C₆₀ for 10 days, acrosome integrity and mitochondrial activity of sperm increased by 18.1% and 34%, respectively, compared with that in the control group. Similarly, the antioxidation abilities and adenosine triphosphate levels in boar sperm treated with carboxylated C₆₀ significantly increased (P ˂ 0.05) compared with those in the control group. The presence of carboxylated C₆₀ in semen extender increases sperm motility probably by suppressing reactive oxygen species (ROS) toxicity damage. Interestingly, carboxylated C₆₀ could protect boar sperm from oxidative stress and energy deficiency by inhibiting the ROS-induced protein dephosphorylation via the cAMP-PKA signaling pathway. In addition, the safety of carboxylated C₆₀ as an alternative antioxidant was also comprehensively evaluated by assessing the mean litter size and number of live offspring in the carboxylated C₆₀ treatment group. Our findings confirm carboxylated C₆₀ as a novel antioxidant agent and suggest its use as a semen extender supplement for assisted reproductive technology in domestic animals.

Resveratrol Improves Boar Sperm Quality via 5'AMP-Activated Protein Kinase Activation during Cryopreservation

Mammalian sperm is highly susceptible to the reactive oxygen species (ROS) stress caused by biochemical and physical modifications during the cryopreservation process. 5′AMP-activated protein kinase (AMPK) is involved in regulating both cell metabolism and cellular redox status. The aim of the present study was to investigate whether the resveratrol protects boar sperm against ROS stress via activation of AMPK during cryopreservation. Boar sperm was diluted with the freezing medium supplemented with resveratrol at different concentrations (0, 25, 50, 75, 100, and 125 μM). It was observed that the addition of 50 μM resveratrol significantly improved the postthaw sperm progressive motility, membrane integrity, acrosome integrity, mitochondrial activity, glutathione (GSH) level, activities of enzymatic antioxidants (glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase), and the phosphorylation of AMPK. Meanwhile, the lipid peroxidation, ROS levels, and apoptosis of postthaw sperm were reduced in the presence of 50 μM resveratrol. Furthermore, when fresh boar sperm was incubated with the medium in the presence of 50 μM resveratrol and 30 μM Compound C (an AMPK inhibitor), the effects of the resveratrol were partly counteracted by the Compound C. These observations suggest that the resveratrol protects boar sperm via promoting AMPK phosphorylation. In conclusion, the addition of resveratrol to the freezing extenders protects boar sperm against ROS damage via promoting AMPK phosphorylation for decreasing the ROS production and improving the antioxidative defense system of postthaw sperm. These findings provide novel insights into understanding the mechanisms of resveratrol on how to protect boar sperm quality contrary to the ROS production during cryopreservation.

Expression of Immune Regulatory Genes in the Porcine Internal Genital Tract Is Differentially Triggered by Spermatozoa and Seminal Plasma

Mating or cervical deposition of spermatozoa or seminal plasma (SP) modifies the expression of genes affecting local immune defense processes at the oviductal sperm reservoir in animals with internal fertilization, frequently by down-regulation. Such responses may occur alongside sperm transport to or even beyond the reservoir. Here, immune-related gene expression was explored with cDNA microarrays on porcine cervix-to-infundibulum tissues, pre-/peri-ovulation. Samples were collected 24 h post-mating or cervical deposition of sperm-peak spermatozoa or SP (from the sperm-peak fraction or the whole ejaculate). All treatments of this interventional study affected gene expression. The concerted action of spermatozoa and SP down-regulated chemokine and cytokine (P00031), interferon-gamma signaling (P00035), and JAK/STAT (P00038) pathways in segments up to the sperm reservoir (utero-tubal junction (UTJ)/isthmus). Spermatozoa in the vanguard sperm-peak fraction (P1-AI), uniquely displayed an up-regulatory effect on these pathways in the ampulla and infundibulum. Sperm-free SP, on the other hand, did not lead to major effects on gene expression, despite the clinical notion that SP mitigates reactivity by the female immune system after mating or artificial insemination.

Aminoguanidine Protects Boar Spermatozoa against the Deleterious Effects of Oxidative Stress

Aminoguanidine is a selective inhibitor of the inducible nitric oxide synthase (iNOS) and a scavenger of reactive oxygen species (ROS). Numerous studies have shown the antioxidant properties of aminoguanidine in several cell lines, but the in vitro effects of this compound on spermatozoa under oxidative stress are unknown. In this study, we tested the hypothesis that aminoguanidine may protect against the detrimental effects of oxidative stress in boar spermatozoa. For this purpose, sperm samples were incubated with a ROS generating system (Fe²⁺/ascorbate) with or without aminoguanidine supplementation (10, 1, and 0.1 mM). Our results show that aminoguanidine has powerful antioxidant capacity and protects boar spermatozoa against the deleterious effects of oxidative stress. After 2 h and 3.5 h of sperm incubation, the samples treated with aminoguanidine showed a significant increase in sperm velocity, plasma membrane and acrosome integrity together with a reduced lipid peroxidation in comparison with control samples (p < 0.001). Interestingly, except for the levels of malondialdehyde, the samples treated with 1 mM aminoguanidine did not differ or showed better performance than control samples without Fe²⁺/ascorbate. The results from this study provide new insights into the application of aminoguanidine as an in vitro therapeutic agent against the detrimental effects of oxidative stress in semen samples.

Removal of seminal plasma prior to liquid storage of boar spermatozoa: A practice that can improve their fertilizing ability

Seminal plasma (SP) plays a vital role in the maintenance of sperm function and integrity along with being involved in their communication with the female reproductive tract. Under in vitro conditions, although it is generally accepted that boar semen is better preserved when SP is diluted (extended) or removed (cryopreserved), its role during storage is not completely elucidated. In this context, the current study sought to determine the role of SP during storage of boar spermatozoa at 17 °C for 72 h. Thus, two treatments were prepared with semen from the sperm-rich fraction (SRF) of boar ejaculate previous to storage in liquid state: 1) PSP: semen directly extended in Beltsville Thawing Solution (BTS), and 2) ASP: semen first centrifuged with subsequent removal of supernatant (containing SP) followed by suspension of sperm in BTS. From this, two experiments were conducted separately in this work: 1) in vitro and 2) in vivo assays. The former aimed to evaluate how sperm capacity responds to in vitro capacitation (IVC) and whether their quality is affected by previous exposure to SP. In the latter, the objective was to understand how important these previous conditions can be for reproductive performance after artificial insemination (AI). According to our results, the previous removal of SP does not affect sperm quality and the response of these cells to IVC (P > 0.05) along with resulting in a lower percentage of acrosome damage in them [12.87 ± 0.76 (ASP) vs. 16.38 ± 0.73 (PSP)] (P < 0.05). This improved preservation of acrosome integrity in the absence of SP can explain the higher fertility rate (%) [63.27 ± 23.47 (ASP) vs. 38.57 ± 16.30 (PSP)] and number of implanted embryos at 28 days after AI (13.71 ± 4.88 (ASP) vs. 7.16 ± 4.02 (PSP)] (P < 0.05) presented by gilts inseminated with seminal doses of ASP. In conclusion, removal of SP prior to liquid storage of boar sperm for 72 h can be beneficial for their fertilizing ability.

Effects of oligomeric proanthocyanidins on quality of boar semen during liquid preservation at 17 °C

The use of antioxidants is an important aspect in the preservation of boar semen. Oligomeric proanthocyanidins (OPC) are an effective natural antioxidants that scavenges free radicals and reactive oxygen species (ROS). This study was designed to investigate the antioxidative effect of OPC on boar semen quality during liquid preservation at 17 °C. The effects of different concentrations of OPC on sperm quality variables, antioxidant effects and fertility were analyzed in this experiment. Semen collected from six Guanzhong-Black boars and was diluted with Beltsville thawing solution (BTS). During the process of liquid preservation at 17 °C, the variables assessed were measured and analyzed every 24 h. The addition of OPC improved boar sperm motility, acrosome integrity, membrane integrity, and mitochondrial membrane potential as compared with that of the control group (P <  0.05). Meanwhile, malondialdehyde content (MDA) and ROS content was less after adding OPC, thereby improving the total antioxidant capacity (T-AOC) (P <  0.05). Different concentrations of OPC have different degrees of protective effects on boar semen quality. The results indicate that 50 μg/mL of OPC was the optimum concentration, and that the conception rate, litter size, and survival rate increased at this concentration as compared with that of the control group (P <  0.05). In summary, the addition of OPC to BTS diluents can improve the quality of boar semen at 17 °C during liquid preservation. Further research is needed to understand the mechanism by which OPC provides protection to boar semen during preservation in vitro.

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

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

Combined effect of apigenin and ferulic acid on frozen-thawed boar sperm quality

The main aim of the present study was to evaluate the cryoprotective effect of apigenin (AP) and ferulic acid (FA) on boar sperm during cryopreservation. AP and FA were both demonstrated to be high-efficiency antioxidants and had not previously been used to protect sperm from cryodamage. As boar sperm is sensitive to oxidative stress, suitable antioxidants are still needed for improving frozen-thawed sperm quality. With this purpose, semen samples coming from five boars were used in this study. Ejaculates of five boars were mixed and split into 16 aliquots, in which different doses of AP and FA were added separately or together. The motility, the plasma membrane integrity, the mitochondrial activity, the acrosomal integrity, the antioxidase activities and the malondialdehyde concentration of the frozen-thawed boar sperm were assessed. The results suggested that both AP and FA significantly improved the frozen-thawed boar sperm quality in all these aspects when they were added to the freezing extender separately, while the highest improvement was recorded when the extender was supplemented with 0.1 mmol/L AP plus 0.15 mmol/L FA. These findings demonstrated that supplementation of freezing extender with both AP and FA had a combined, beneficial effect on frozen-thawed boar sperm.

Seminal plasma antioxidants are directly involved in boar sperm cryotolerance

Boar ejaculates are ejected in fractions with a specific composition in terms of sperm numbers and seminal plasma (SP), which is reflected in the varying sperm cryotolerance observed among different fractions. As boar sperm are particularly sensitive to oxidative stress, this study evaluated the role of SP antioxidants in the observed differences in sperm cryotolerance among ejaculate fractions. Ten ejaculates from five boars were manually collected in fractions: the first 10 mL of the sperm-rich fraction (SRF), the rest of the SRF and the post-SRF. Semen samples comprising the entire ejaculate (EE) were created by proportionally mixing the three fractions described above. Each of the 40 resulting semen samples was split into two aliquots: one was used for sperm cryopreservation following a standard protocol utilizing 0.5-mL straws, and the other was used to collect SP for antioxidant assessment. Frozen-thawed (FT) sperm from the SRF (the first 10 mL of the SRF and the rest of the SRF) and those from post-SRF were of the highest and worst quality, respectively, which was measured in terms of total and objective progressive motility and viability (P < 0.01). Viable FT sperm from the post-SRF generated more reactive oxygen species and experienced more lipid peroxidation than those from the SRF (both the first 10 mL and the rest of the SRF) (P < 0.01). The percentage of FT sperm exhibiting fragmented nuclear DNA did not differ among ejaculate fractions and the EE. Catalase, glutathione peroxidase and glutathione peroxidase 5 (GPx-5) were lowest in SP from the first 10 mL of the SRF (P < 0.001), whereas superoxide dismutase (SOD) and paraoxonase 1 (PON-1) were highest in SP of the SRF (both the first 10 mL and the rest of the SRF) (P < 0.01). Trolox-equivalent antioxidant capacity (TEAC) and the ferric-reducing ability of plasma (FRAP) were highest in SP from the first 10 mL of the SRF and lowest in the post-SRF (P < 0.001), whereas cupric-reducing antioxidant capacity was lowest (P < 0.05) in SP from the first 10 mL of the SRF. Regression analyses indicated that certain SP antioxidants had good predictive value for post-thaw recovery rates of total motility (R² = 54.8%, P < 0.001; including SOD, TEAC and FRAP) and viability (R² = 56.1%, P < 0.001; including SOD, PON-1, GPx-5 and TEAC). These results demonstrated that certain SP antioxidants are positively involved in boar sperm cryotolerance, minimizing the oxidative stress imposed by cryogenic handling.

Rooibos (Aspalathus linearis) extract enhances boar sperm velocity up to 96 hours of semen storage

Rooibos (Aspalathus linearis) is a native shrub from South African fynbos and has become very popular in the last decades for its antioxidant and medicinal attributes. Several studies have shown its beneficial properties in numerous cell lines, but to date, the in vitro effects of rooibos extract on sperm cells are still unknown. In this study, boar semen was supplemented with four concentrations both of fermented and unfermented rooibos extracts during 96 h of liquid storage at 17°C. The effects of rooibos extracts on sperm velocity, membrane integrity, and acrosomal status were evaluated at 2 h, 48 h, and 96 h of semen storage. Overall our results indicate that rooibos extract enhances sperm velocity, protects the acrosome structure, and tends to preserve the membrane integrity during semen storage. Although the unfermented rooibos showed higher total polyphenol content and total antioxidant capacity than the fermented one, the latter had better effects on sperm velocity leading to, for instance, an increase of 30% in the rectilinear velocity (VSL) at 48 h compared to the control group. Taking into account the different storage times, we established a suitable range of extracts concentrations to be used in boar semen. The rooibos extract ought to be considered as a powerful and natural source of antioxidants for the preservation of boar semen.

The cryoprotective effect of iodixanol in buffalo semen cryopreservation

This is the first report to examine the effect of iodixanol (OptiPrep^TM) on cryosurvival of buffalo spermatozoa. A total of thirty ejaculates (five ejaculates from each bull) from six buffalo bulls were used for this experiment. Each ejaculate was divided into four aliquots and diluted in freezing extender supplemented with different concentrations of OptiPrep^TM (0, 1.25, 2.5 and 5%) and then cryopreserved. The semen quality variables were evaluated before and after freezing of the semen. There were no effects of OptiPrep^TM (P>0.05) on sperm kinetics, motility, abnormality and membrane integrity of fresh extended spermatozoa. However, after freeze-thaw, sperm motility, plasma membrane integrity and distance travelled in cervical mucus of 2.5% OptiPrep^TM treated samples showed significantly higher (P<0.05) compared to other treated and control samples. No significant differences (P>0.05) were seen in sperm abnormality and acrosomal integrity of treated and control frozen-thawed samples. The total antioxidant capacity of 2.5 and 5% OptiPrep^TM treated frozen-thawed sperm were found to be higher (P<0.05) as compared to other groups; whereas the MDA level in OptiPrep^TM treated sperm was significantly lower than the control (P<0.05). In incubation test, 2.5% OptiPrep^TM proved to be better in preservation of sperm motility as compared to other treated and control samples. In conclusion, the present study has shown that iodixanol has the ability protect spermatozoa against oxidative stress and resulting overall improvement in the post-thaw semen quality.

Glutathione Peroxidase 5 Is Expressed by the Entire Pig Male Genital Tract and Once in the Seminal Plasma Contributes to Sperm Survival and In Vivo Fertility

Glutathione peroxidase-5 (GPX5) is an H₂O₂-scavenging enzyme identified in boar seminal plasma (SP). This study attempted to clarify its origin and role on sperm survival and fertility after artificial insemination (AI). GPX5 was expressed (Western blot and immunocytochemistry using a rabbit primary polyclonal antibody) in testes, epididymis and accessory sex glands (6 boars). SP-GPX5 concentration differed among boars (11 boars, P < 0.001), among ejaculates within boar (44 ejaculates, P < 0.001) and among portions within ejaculate (15 ejaculates). The first 10 mL of the sperm rich fraction (SRF, sperm-peak portion) had a significantly lower concentration (8.87 ± 0.78 ng/mL) than the rest of the SRF and the post-SRF (11.66 ± 0.79 and 12.37 ± 0.79 ng/mL, respectively, P < 0.005). Sperm motility of liquid-stored semen AI-doses (n = 44, at 15–17°C during 72h) declined faster in AI-doses with low concentrations of SP-GPX5 compared to those with high-levels. Boars (n = 11) with high SP-GPX5 showed higher farrowing rates and litter sizes than those with low SP-GPX5 (a total of 5,275 inseminated sows). In sum, GPX5 is widely expressed in the boar genital tract and its variable presence in SP shows a positive relationship with sperm quality and fertility outcomes of liquid-stored semen AI-doses.