Vitamin E Analogue Improves Rabbit Sperm Quality during the Process of Cryopreservation through Its Antioxidative Action

Sperm freezing damage: the role of regulated cell death

Substantial progress in research on sperm cryopreservation has occurred since the twentieth century, especially focusing on improving sperm freezing procedures and optimizing semen extenders. However, the cellular biological mechanisms of sperm freezing damage are still unclear, which greatly restricts the promotion and development of sperm cryopreservation. An essential component of sperm freezing damage is the occurrence of cell death. Considering the existence of multiple types of cell death pathways, this review discusses connections between characteristics of regulated cell death (e.g., apoptosis and ferroptosis), and accidental cell death (e.g., intracellular ice crystals) with sperm freezing damage and explores possible future research directions in this field.

Pyrroloquinoline Quinone Improves Ram Sperm Quality through Its Antioxidative Ability during Storage at 4 °C

Sperm motility is an important factor in the migration of sperm from the uterus to the oviduct. During sperm preservation in vitro, sperm generates excessive ROS that damages its function. This study aims to investigate whether the addition of pyrroloquinoline quinone (PQQ) to the diluted medium could improve chilled ram sperm quality, and then elucidates the mechanism. Ram semen was diluted with Tris-citric acid-glucose (TCG) medium containing different doses of PQQ (0 nM, 10 nM, 100 nM, 1000 nM, 10,000 nM), and stored at 4 °C. Sperm motility patterns, plasma membrane integrity, acrosome integrity, mitochondrial membrane potential, reactive oxygen species (ROS) levels, malondialdehyde (MDA) levels, superoxide dismutase (SOD) activity, and ATP levels were measured after preservation. Furthermore, the expressions of NADH dehydrogenase 1 (MT-ND1) and NADH dehydrogenase 6 (MT-ND6) in sperm were also detected by western blotting. In addition, sperm capacitation and the ability of sperm to bind to the zona pellucina were also evaluated. It was observed that the addition of PQQ significantly (p < 0.05) improved ram sperm motility, membrane integrity, and acrosome integrity during preservation. The percentage of sperm with high mitochondrial membrane potential in the PQQ treatment group was much higher than that in the control. In addition, supplementation of PQQ also decreased the sperm MDA and ROS levels, while increasing ATP levels. Interestingly, the levels of MT-ND1 and MT-ND6 protein in sperm treated with PQQ were also higher than that of the control. Furthermore, the addition of 100 nM PQQ to the medium decreased ROS damage in MT-ND1 and MT-ND6 proteins. The addition of 100 nM PQQ significantly (p < 0.05) increased protein tyrosine phosphorylation in ram sperm after induced capacitation. Furthermore, the value of the sperm-zona pellucida binding capacity in the 100 nM PQQ treatment group was also much higher than that of the control. Overall, during chilled ram- sperm preservation, PQQ protected ram sperm quality by quenching the ROS levels to reduce ROS damage and maintain sperm mitochondrial function, and preserved the sperm's high ability of fertilization.

Effects of sodium selenite, cysteamine, bacterially synthesized Se-NPs, and cysteamine loaded on Se-NPs on ram sperm cryopreservation

During the cryopreservation of sperm, the production of highly reactive oxygen species (ROS) can reduce their viability and fertility. However, the addition of antioxidants can help reduce the harmful effects of ROS. One such antioxidant is selenium, which is a co-factor of the glutathione peroxidase enzyme that is effective in scavenging ROS. Cysteamine can also take part in the structure of this enzyme. The use of nanoparticles can be less toxic to cells than their salt form. To this end, researchers synthesized Se-NPs using the streptococcus bacteria and loaded cysteamine onto the synthesized Se-NPs. The biosynthesis of Se-NPs and cysteamine loaded on Se-NPs was confirmed by UV-visible spectroscopy, X-ray diffraction (EDX), Fourier transforms infrared (FTIR) spectroscopy, and Field Emission Scanning Electron Microscope (FE-SEM). For cryopreservation, ram semen samples were diluted, and different concentrations (0, 1, 5, 25, and 125 µg/mL) of cysteamine, Se-NPs, cysteamine loaded on Se-NPs, and sodium selenite were added. An extender containing no supplement was considered as control group. After cooling the semen samples, they were frozen and stored in liquid nitrogen for evaluation. The samples were thawed and analyzed for mobility, viability, membrane and DNA integrity, and sperm abnormalities, as well as malondialdehyde level (MDA) and superoxide dismutase (SOD). The data was processed using SPSS, and a significance level of p < 0.05 was considered. The results of this experiment showed that adding 1 μg/mL of cysteamine loaded on Se-NPs to the diluent significantly increased the motility, viability, and membrane integrity and SOD of spermatozoa compared to the other treatment groups and control group, and reduced the abnormality, apoptosis, and MDA level of spermatozoa in comparison with the other treatment groups and control group (p < 0.05). In conclusion, the addition of cysteamine loaded on Se-NPs was found to improve the quality of ram sperm after cryopreservation.

Influence of nano-formulations of clove bud (Syzygium aromaticum) extract on freezing ability, antioxidant capacity, caspase-3 activity, acrosome reaction and fertility of frozen rabbit semen

The current study aimed to investigate the impact of nano-formulations of clove bud ethanolic extract (CBENF) in the extender on sperm characteristics, antioxidant capacity, oxidative biomarkers, enzymatic activity, apoptosis and fertility of post-thawed rabbit semen. Twelve mature male rabbits semen samples were pooled and cryopreserved in a Tris-egg yolk-based extender containing varying concentrations of CBENF (0, 25, 50, 75 and 100 μg/mL). After the equilibration and freezing-thawing process, CBENF (100 μg /mL) significantly enhanced progressive motility, viability and membrane integrity. Conversely, sperm abnormality was significantly reduced by CBENF supplementation. Total antioxidant capacity was increased in the post-thawed sperm medium, while nitric oxide and malondialdehyde were decreased in all CBENF concentrations. The lactic dehydrogenase and caspase-3 activities were decreased, whereas the number of live spermatozoa with an intact acrosome was increased in all CBENF concentrations. Conception rate and litter size per doe were higher in doe rabbits inseminated with semen supplemented with 100 μg CBENF/mL than un-supplemented group (76% vs. 52% and 8.4 vs. 7.7/doe), with no statistical differences. These findings suggest that supplementing rabbit extenders with 100 μg of CBENF/mL could be an effective strategy for enhancing freeze-thawing rabbit sperm attributes and fertility.

Effect of sulforaphane on long-term storage of rabbit semen

In this study, it was aimed to determine the effect of sulforaphane (SFN) on rabbit semen cryopreservation. Semen collected from animals was divided into 5 equal volumes as Control, SFN 5 µM, SFN 10 µM, SFN 25 µM and SFN 50 µM groups. Afterwards, semen analyzes were performed. According to our results, there was no statistical difference between the groups at 4°C. However after freezing thawing, the highest total motility, progressive motility and rapid spermatozoa rate was seen in the 10 µM SFN group, while the lowest was observed in the 50 µM SFN group (P<0.05). Static sperm ratio was highest in the 50 µM group, while the lowest was observed in the 10 µM SFN group. When flow cytometry results examined the rate of acrosomal damaged and dead sperm was the lowest in the 10 µM SFN group, a statistical difference was observed between the control group (P<0.05). The highest rate of sperm with high mitochondrial membrane potential was seen in the 5 µM SFN and 10 µM SFN groups. Apoptosis and ROS rates were found to be lower in the experimental groups compared to the control groups (P<0.05). As a result, SFN supplementation at a dose of 10 µM increased the quality of sperm in the freezing and thawing processes of rabbit semen. In conclusion, 10 µM SFN improved the quality of cryopreservation of rabbit semen.

The protective effects of astaxanthin on pre-antral follicle degeneration in ovine vitrified/warmed ovarian tissue

This study assesses the protective effects of astaxanthin (AST) against vitrification/warming-induced cryoinjuries of ovarian tissue slices in sheep. Cortical slices of slaughterhouse acquired-ovine ovaries were randomly distributed in different groups: fresh, toxicity, and five vitrification groups including vitrification in presence of 0 (control group), 1, 10 and 100 μM astaxanthin or 100 μM vitamin E. After vitrification/warming and 24 h culturing, the samples were subjected to histological studies, antioxidant evaluation by TAC and TBAR assays, and assessment of relative expression of BMP4, BMP15, GDF9 and KITLG genes related to folliculogenesis and follicular growth regulation. According to the results, vitrification reduced the percentage of morphologically intact follicles compared to the fresh and toxicity groups (p < 0.05). In vitrification groups, vitamin E and all three concentrations of AST increased the percentage of intact pre-antral follicles and antioxidant activity relative to the vitrified control (p < 0.05). This enhancement significantly occurred in 10 μM AST group more than vitamin E (p < 0.05). Also, 10 μM concentration of AST enhanced the expression of all the examined genes compared to the control (p < 0.05), while the expression of BMP4, BMP15 and KITLG was higher in the AST than vitamin E (p < 0.05). The latter could increase only the expression of GDF9 compared to the control group (p = 0.011). In conclusion, AST is a highly effective antioxidant for maintaining the survival of pre-antral follicles, retaining cell density, increasing total antioxidant capacity, and increasing the expression of some genes related to follicular development after short-term culture of vitrified/warmed ovarian tissue slices.

The effects of melatonin, glutathione and vitamin E on semen cryopreservation of Mediterranean buffalo

The aim of this study was to investigate the effects of melatonin (MLT), reduced glutathione (GSH) and vitamin E (Vit. E) or their combinations on semen cryopreservation of Mediterranean buffalo. The quality parameters such as viability, abnormality rate, motility, structural integrity and the antioxidant capacity of frozen-thawed sperm were evaluated. The efficiency of frozen-thawed sperms in performing their functions was further analyzed by in vitro fertilization (IVF). In those separately supplemented groups, 0.2 mg/mL MLT, 0.2 mM GSH and 0.4 mg/mL Vit. E had the best effect on antioxidant capacity, kinetics and morphology, respectively. In addition, the cleavage, blastocyst and hatching blastocyst rates of IVF embryos were higher in 0.2 mg/mL MLT, 0.2 mM GSH, 0.2 and 0.4 mg/mL Vit. E groups than the blank control. Among the three combination groups, the kinetics and structure integrity of frozen-thawed sperms, cleavage, blastocyst and hatching blastocyst rates of IVF embryos were higher in 0.4 mg/mL Vit. E plus 0.2 mg/mL MLT group than the blank control group, revealed that this combination had comprehensive protection on frozen-thawed sperm of Mediterranean buffalo. These results support to develop special semen freezing extender containing an optimal choice of MLT, GSH and Vit. E, and to enhance the efficiency of frozen-thawed sperm of Mediterranean buffalo for IVF.

Metabolomic analysis reveals spermatozoa and seminal plasma differences between Duroc and Liang guang Small-spotted pig

The Liang guang Small-spotted pig is a well-known Chinese indigenous pig that is valued for its exceptional meat quality. However, the Liang guang Small-spotted pig has a lower semen storage capacity, shorter storage time and worse semen quality compared to Duroc. Pig sperm used for artificial insemination (AI) loses part of vitality and quality when being stored in commercial solutions. Serious vitality losses and short shelf life of the semen are particularly prominent in Liang guang Small-spotted pig. In this study, the metabolites in seminal plasma and spermatozoa of Duroc and Liang guang Small-spotted pigs were identified using UHPLC-Q-TOF/MS technology. The findings indicated forty distinct metabolites concentrating on energy metabolic substrates and antioxidant capacity in Liang guang Small-spotted pig and Duroc seminal plasma, including D-Fructose, succinate, 2-dehydro-3-deoxy-d-gluconate, alanine betaine, citrate, carnitine, acetylcarnitine and so on. Seventeen different metabolites were explored, with a focus on glycerophospholipid metabolism in Liang guang Small-spotted pig and Duroc spermatozoa, primarily including glycerol 3-phosphate, acetylcarnitine, phosphatidylcholine (PC) 16:0/16:0, palmitoyl sphingomyelin, acetylcholine, choline, glycerophosphocholine, betaine, L-carnitine, creatinine and others. This study reveals the metabolite profile of spermatozoa and seminal plasma among different pig breeds and might be valuable for understanding the mechanisms that lead to sperm storage capacity. Metabolites involved in energy metabolism, antioxidant capacity and glycerophospholipid metabolism might be key to the poor sperm storage capacity in Liang guang Small-spotted pig.

Effects of riboflavin on boar sperm motility, sperm quality, enzyme activity and antioxidant status during cryopreservation

Objectives

This study was conducted to evaluate the effect of adding riboflavin to boar sperm freezing extender on the challenge of cryopreservation.

Methods

Different concentrations (0, 5, 10, 15, 20 or 25 μM) of riboflavin were added to the freezing extender. Spermatozoa motility, membrane integrity, acrosomal integrity, mitochondrial membrane potential and enzyme activities were analysed once 10 min after thawing. Q‐PCR was used to detect the mRNA expression of Caspase3, Bcl‐2 and Bax.

Results

The results showed that the addition of 10 μM riboflavin to boar sperm freezing extender significantly increased the frozen‐thawed sperm progressive motility compared with the control group (p < 0.05). Activities of superoxide dismutase, glutathione peroxidase and catalase improved after adding riboflavin to the extender (p < 0.05). During freezing‐thawing, the boar sperm mitochondrial membrane potential, acrosomal integrity, plasma membrane and DNA at 10 μM in the riboflavin group increased by 6.6%, 9.6%, 5.49% and 5.62% (p < 0.05), respectively, compared with the control group. The addition of 10 μM riboflavin to the extender significantly decreased the malondialdehyde (p < 0.05) content, whereas it increased the ATP content (p < 0.05) of boar sperm during freezing‐thawing. Furthermore, the expression of Caspase‐3 and Bax (p < 0.05) were significantly lower, whereas the expression of BCL‐2 (p < 0.05) was greater than the control group when adding 10 μM riboflavin to the extender.

Conclusions

Riboflavin showed cryoprotective capacity to the freezing extender used for boar sperm during the process of freezing‐thawing, and the optimal concentration of riboflavin for the frozen extender was 10 μM.

Reducing the Glucose Level in Pre-treatment Solution Improves Post-thaw Boar Sperm Quality

Frozen–thawed boar sperm was not widely used in pig artificial insemination as the sperm quality was damaged by biochemical and physical modifications during the cryopreservation process. The aim of this study was to investigate whether reduction of the glucose level in diluted medium could protect the post-thaw boar sperm or not. Boar sperm was diluted with the pre-treatment medium with different doses of glucose (153, 122.4, 91.8, 61.2, 30.6, and 0 mM) during the cooling process. The sperm motility patterns and glycolysis were evaluated during the cooling process. Meanwhile, the post-thaw sperm quality, ATP level, mitochondrial function as well as apoptosis were also measured. It was observed that 153 mM glucose treatment showed the highest glycolysis in boar sperm as the activities of hexokinase, fructose-bisphosphate aldolase A, and lactate dehydrogenase are the highest as well as the lactate level. Reduction of the glucose level from 153 to 30.6 mM suppressed sperm glycolysis. In addition, treatment with 153 mM glucose made the sperm demonstrate a circle-like movement along with a high value of curvilinear velocity and amplitude of the lateral head, while decreasing the glucose level reduced those patterns in the cooling process. Moreover, reduction of the glucose level also significantly increased the post-thaw sperm's total motility, progressive motility, straight-linear velocity, membrane integrity, and acrosome integrity. The treatment with 30.6 mM glucose showed the highest value among the treatments. Furthermore, the post-thaw sperm's succinate dehydrogenase activity, malate dehydrogenase activity, mitochondrial membrane potential as well as ATP level were increased by reducing the glucose level from 153 to 30.6 mM. Interestingly, the treatment with 30.6 mM glucose showed the lowest apoptosis of post-thaw sperm among the treatments. Those observations suggest that reduction of the glucose level in diluted medium increased the post-thaw boar sperm quality via decreasing the glycolytic metabolism. These findings provide novel insights that reduction of boar sperm activity via decreasing sperm glycolysis during the cooling process helps to improve the post-thaw sperm quality during cryopreservation.

Resveratrol and lycium barbarum polysaccharide improve Qinling giant panda (Ailuropoda melanoleuca Qinlingensis) sperm quality during cryopreservation

Background

Semen cryopreservation has become an essential tool for conservation efforts of the giant panda (Ailuropoda melanoleuca); however, it is severely detrimental to sperm quality. Evidence has shown that antioxidants have the potential to reverse cryopreservation-induced damage in sperm. The purpose of this study was to screen effective antioxidants that could retain sperm quality during cryopreservation and to determine the optimal dose. Seven antioxidant groups, including resveratrol (RSV = 50 μM, RSV = 100 μM, RSV = 150 μM), lycium barbarum polysaccharide (LBP = 2 mg/mL, LBP = 4 mg/mL), laminaria japonica polysaccharides (LJP = 1 mg/mL) or combination (LBP = 2 mg/mL, LJP = 1 mg/mL and RSV = 100 μM) were assessed.

Results

RSV, LBP, LJP, or a combination of RSV, LBP, and LJP added to the freezing medium significantly improved sperm progressive motility, plasma membrane integrity, acrosome integrity, and mitochondrial activity during the cryopreservation process. Furthermore, the activities of glutathione peroxidase and superoxide dismutase were also improved. The levels of reactive oxygen species and malondialdehyde in semen were notably reduced. Hyaluronidase activity and acrosin activity were significantly increased in LBP-treated sperm. However, sperm total motility and DNA integrity were not significantly different between the groups.

Conclusions

RSV (50 μM) or LBP (2 mg/mL) are the best candidate antioxidants for inclusion in the freezing medium to improve the quality of giant panda spermatozoa during semen cryopreservation.

Pre-treatment of ram semen extender with magnetic nanoparticles on freeze-thawed spermatozoa

Background

Extensive use of different nanoparticles caused significant concerns about their biological safety.

Objective

This study aimed to evaluate the effects of cryopreservation on ram semen after adding magnetic nanoparticles (MNPs) to separate X and Y chromosome‐bearing spermatozoa.

Methods

The experimental ram sperms in this research included treated spermatozoa (50 μg/ml MNPs) and non‐treated spermatozoa. DNA damage of spermatozoa was examined using an acridine orange (AO) assay. Sperm viability, membrane functionality, abnormality and malondialdehyde (MDA) level were also measured.

Results

Results indicated that the pre‐treatment of ram semen extender with MNPs did not significantly affect the semen parameters such as viability, membrane functionality, abnormality, as well as lipid peroxidation (LPO) levels and DNA integrity in comparison with the control group (p < 0.05).

Conclusions

These observations suggest that pre‐treatment of ram semen extender with MNPs after semen sexing did not have adverse effects on different semen parameters after cryopreservation.

In the current study, we evaluated the effects of cryopreservation on ram semen after adding magnetic nanoparticles (MNPs), then after thawing some semen parameters were evaluated.

The cryoprotective effect of vitamins on human spermatozoa quality: a systematic review and meta-analysis

The Cryopreservation of spermatozoa ensures preserving fertility potential after some medical treatments such as chemotherapy and radiotherapy in cancer patients. However, many spermatozoa encounter serious damages, and their motility and viability decrease considerably after thawing. The excessive production of reactive oxygen species is one of the major causes of these damages. The supplementation of cryopreservation media with vitamins, which are well-known antioxidants, can reduce cryopreservation-induced damages. In this systematic review, we aimed to evaluate the cryoprotective effect of various vitamins on the quality of cryopreserved-thawed human spermatozoa. Two researchers searched PubMed, ISI, and Scopus databases up to March 2020. All original articles using vitamins in human spermatozoa cryopreservation media were included. We used a standardized form to extract sample size and to determine sample quality, the type and dose of vitamins, and the cryopreservation methods and their effects. We performed a meta-analysis on studies with available data (Mean + SD in cryoprotectant and cryoprotectant + cryoprotectant groups). We also performed a test of between-study heterogeneity, subgroup analysis, and meta-regression. Out of 258 studies, 16 articles were included for the analysis. Our meta-analysis revealed that using vitamins in cryopreservation media could increase motility by 4.60% (95% CI 6.16, 3.05; P = 0.0001), viability by 5.71% (95% CI 9.71, 1.72; P = 0.0001), and DNA integrity by 10.20% (95% CI 12.98, 7.42; P = 0.0001) in cryopreserved-thawed spermatozoa. We found a significant correlation between using vitamins and improved spermatozoa quality; the sperm motility and viability were improved and DNA fragmentation was reduced after thawing by vitamins. However, we could not emphasize on any type or dose of vitamins but we conclude that the anti-oxidative function of vitamins is the main reason for these benefits.

Improving the post-thaw quality of rooster semen using the extender supplemented with resveratrol

Avian spermatozoa are highly susceptible to reactive oxygen species (ROS) produced during the cryopreservation. The aim of the current study was to investigate the antioxidant effects of resveratrol (RSV) during rooster semen cryopreservation. Changes in expression of AMP-activated protein kinase as a possible mechanism behind the beneficial effects of resveratrol were also evaluated. Semen samples were collected from ten Ross broiler breeders (52-wk) using abdominal massage, then divided into 4 equal aliquots and cryopreserved in Beltsville extender that contained different concentrations (0 µM, 0.01µM, 0.1µM, and 1µM) of RSV. higher percentage (P < 0.05) of total motility and membrane integrity was observed in RSV-0.1 compared to the other frozen groups. Moreover, higher percentage of sperm mitochondrial activity was observed in the RSV-0.01 and RSV-0.1 compared to the frozen control (P < 0.05). The lowest percentage of apoptotic like changes was found in the RSV-0.1 in comparison to the other groups (P < 0.05). RSV-0.01 and RSV-1 groups produced the lowest levels of H2O2 and O2- compared to the other frozen groups, respectively. Malondialdehyde (MDA) concentration, velocity average path (VAP), and linearity (LIN) were not affected by different concentrations of RSV (P > 0.05). We observed a dose-dependent increase in AMP-activated protein kinase expression in groups exposed to RSV. Thus, RSV-1 increased AMP-activated protein kinase phosphorylation but had no positive effects on post thaw sperm parameters. Our findings suggest that RSV-0.1 improve thawed sperm functions, and these effects might be mediated through activation of AMP-activated protein kinase.

Cysteine improves boar sperm quality via glutathione biosynthesis during the liquid storage

Objective

Sperm are particularly susceptible to reactive oxygen species (ROS) stress. Glutathione (GSH) is an endogenous antioxidant that regulates sperm redox homeostasis. However, it is not clear whether boar sperm could utilize cysteine for synthesis GSH to protect sperm quality from ROS damage. Therefore, the present study was undertaken to elucidate the mechanism of how cysteine is involved in protecting boar sperm quality during liquid storage.

Methods

Sperm motility, membrane integrity, lipid peroxidation, 4-hydroxyIlonenal (4-HNE) modifications, mitochondrial membrane potential, as well as the levels of ROS, GSH and, ATP were evaluated. Moreover, the enzymes (GCLC: glutamate cysteine ligase; GSS: glutathione synthetase) that are involved in glutathione synthesis from cysteine precursor were detected by western blotting.

Results

Compared to the control, addition of 1.25 mM cysteine to the liquid storage significantly increased boar sperm progressive motility, straight-line velocity (VSL), curvilinear velocity (VCL), beat-cross frequency (BCF), membrane integrity, mitochondrial membrane potential, ATP level, acrosome integrity, activities of superoxide dismutase (SOD) and catalase, and GSH level, while reducing the ROS level, lipid peroxidation and 4-HNE modifications. It was also observed that the GCLC and GSS were expressed in boar sperm. Interestingly, when we used menadione to induce sperm with ROS stress, the menadione associated damages were observed to be reduced by the cysteine supplementation. Moreover, compared to the cysteine treatment, the γ-GCS activity, GSH level, mitochondrial membrane potential, ATP level, membrane integrity and progressive motility in boar sperm were decreased by supplementing with an inhibitor of GSH synthesis, buthionine sulfoximine (BSO).

Conclusion

These data suggest that boar sperm could biosynthesize the GSH from cysteine in vitro. Therefore, during storage, addition of cysteine improves boar sperm quality via enhancing the GSH synthesis to resist ROS stress.

Factors affecting rabbit sperm cryopreservation: a mini-review

Rabbits are an important animal species for meeting the nutritional requirements of the world's growing population due to the high conversion rate of feed. In most countries, the rabbit industry currently relies on artificial insemination with fresh or chilled and frozen-thawed spermatozoa. Various factors during the freezing process, including diluents, sperm preparation and freezing techniques, antioxidants, sudden temperature changes, ice formation and osmotic stress, have been proposed as reasons for the poor sperm quality post thaw. Despite the extensive progress reached in the field of rabbit sperm cryopreservation, new methodological approaches that could overcome problems in sperm cryopreservation are necessary. The aim of this review was to describe the factors that affect the cryopreservation of rabbit sperm.

Protective Effect of Chlorogenic Acid on Human Sperm: In Vitro Studies and Frozen-Thawed Protocol

The study evaluated the chlorogenic acid (CGA) antioxidant potential on oxidative stress (OS) induced in vitro in human spermatozoa and during cryopreservation procedure. Swim-up selected spermatozoa were treated with 100 µM CGA, 100 µM H₂O₂ to induce lipid peroxidation (LPO), and with both compounds and the effects on mitochondrial membrane potential (MMP) by JC-1, DNA integrity by acridine orange (AO), and sperm ultrastructure by transmission electron microscopy (TEM), were evaluated. CGA antioxidant activity was assessed by measuring malondialdehyde (MDA) and F₂-isoprostanes (F₂-IsoPs) in the media. The CGA protective activity and the immunolocalization of Phospho-AMPKα (Thr172) were explored in frozen-thawed sperm. CGA was not toxic for sperm motility, DNA integrity and MMP. The increase in MDA (p < 0.05) and F₂-IsoPs (p < 0.001), DNA damage (p < 0.01) and low MMP (p < 0.01) levels after H₂O₂ treatment were reduced in presence of CGA as well as the percentage of broken plasma membranes (p < 0.01) and altered acrosomes (p < 0.01) detected by TEM. Treated frozen-thawed spermatozoa showed increased sperm motility (p < 0.01), DNA integrity (p < 0.01), MMP (p < 0.01), reduced MDA (p < 0.01) and increased sperm percentage with Phospho-AMPKα labelling in the head (p < 0.001). CGA can be used to supplement culture media during semen handling and cryopreservation where OS is exacerbated.

Strategies for Highly Efficient Rabbit Sperm Cryopreservation

The rabbit is a valuable animal for both the economy and biomedical sciences. Sperm cryopreservation is one of the most efficient ways to preserve rabbit strains because it is easy to collect ejaculate repeatedly from a single male and inseminate artificially into multiple females. During the cooling, freezing and thawing process of sperms, the plasma membrane, cytoplasm and genome structures could be damaged by osmotic stress, cold shock, intracellular ice crystal formation, and excessive production of reactive oxygen species. In this review, we will discuss the progress made during the past years regarding efforts to minimize the cell damage in rabbit sperms, including freezing extender, cryoprotectants, supplements, and procedures.

Mitochondrial Dysfunction and Oxidative Stress Caused by Cryopreservation in Reproductive Cells

Mitochondria, fundamental organelles in cell metabolism, and ATP synthesis are responsible for generating reactive oxygen species (ROS), calcium homeostasis, and cell death. Mitochondria produce most ROS, and when levels exceed the antioxidant defenses, oxidative stress (OS) is generated. These changes may eventually impair the electron transport chain, resulting in decreased ATP synthesis, increased ROS production, altered mitochondrial membrane permeability, and disruption of calcium homeostasis. Mitochondria play a key role in the gamete competence to facilitate normal embryo development. However, iatrogenic factors in assisted reproductive technologies (ART) may affect their functional competence, leading to an abnormal reproductive outcome. Cryopreservation, a fundamental technology in ART, may compromise mitochondrial function leading to elevated intracellular OS that decreases sperm and oocytes' competence and the dynamics of fertilization and embryo development. This article aims to review the role played by mitochondria and ROS in sperm and oocyte function and the close, biunivocal relationships between mitochondrial damage and ROS generation during cryopreservation of gametes and gonadal tissues in different species. Based on current literature, we propose tentative hypothesis of mechanisms involved in cryopreservation-associated mitochondrial dysfunction in gametes, and discuss the role played by antioxidants and other agents to retain the competence of cryopreserved reproductive cells and tissues.

Multiparametric Study of Antioxidant Effect on Ram Sperm Cryopreservation-From Field Trials to Research Bench

Simple Summary

The use of antioxidant compounds could be a successful tool to improve sperm cryopreservation protocols in ovine species. These molecules have been widely employed in different mammalian species with this purpose. It is important to consider the existence of a species-specific antioxidant effect discarding the extrapolations from other animal species. To corroborate the real effectiveness of these compounds is important to combine two approaches: in vitro sperm quality analyses and in vivo field trials based on fertility. In the first scenario, a multiparametric analyses and novel tests based on spermatozoa redox balance, as the main target of antioxidants, could improve the accuracy on antioxidant effectiveness on sperm quality. Moreover, an extensive field insemination study provides the definitive tool to select the best antioxidant treatment. All these aspects have been applied and extensively discussed throughout this manuscript. Novel approaches have been incorporated, such as RedoxSYS, to provide more accuracy in the integrative studies of Redox status in spermatozoa. The effectiveness of an antioxidant treatment, as trolox in our study, should be demonstrated in an integrative way, from in vivo (fertility trials) to in vitro analyses (sperm quality assays), especially when the final aim is to reach AI implementation.

Abstract

The optimization of sperm cryopreservation protocols in ram is a feasible tool to reinforce artificial insemination technologies considering the desirable application of sperm by vaginal/cervical or transcervical deposition. Cryopreservation provokes different types of damage on spermatozoa and many of these detrimental effects are triggered by redox deregulation. For this reason, the antioxidant supplementation in sperm cryopreservation protocols to decrease reactive oxygen species (ROS) levels and to equilibrate redox status has been widely employed in different species. Despite this, more fertility trials are necessary to provide the definitive tool to ensure the antioxidant effectiveness on sperm quality. For this reason, in this work, we performed a multiparametric analysis of some previously tested antioxidants (crocin, GSH and Trolox) on ram sperm cryopreservation from field trials to sperm quality analyses focused on new strategies to measure redox balance. Attending to fertility trial, Trolox supplementation registered an improvement concerning to fertility (when we considered high fertility males) and multiple lambing frequency and other complementary and descriptive data related to lambing performance such as prolificacy and fecundity. This positive effect was more evident in multiple lambing frequency when we considered low fertility males than in global male analysis. In vitro analyses of sperm quality confirmed in vivo trials registering a positive effect on sperm viability and redox balance. In this study, we provided the definitive evidence that the role of trolox on redox balance maintenance has a direct effect on fertility parameters, such as prolificacy. The effectiveness of antioxidant treatments was tested, for the first time in ovine species, using an integrative and multiparametric approach combining in vivo and in vitro analyses and novel approaches, such as RedoxSYS. These types of strategies should be applied to improve sperm conservation methods and optimize AI technologies upgrading the correlation between in vitro and in vivo analyses.

Melatonin can improve viability and functional integrity of cooled and frozen/thawed rabbit spermatozoa

Melatonin is known to protect sperm against freezing-inflicted damage in different domestic species. The aim of the study was to evaluate the effect of supplementation of semen extender with melatonin on the quality and DNA integrity of cooled and frozen/thawed rabbit spermatozoa. We also investigated whether the addition of melatonin to the semen extender could improve the fertility of rabbit does artificially inseminated with frozen/thawed semen. Semen samples collected from eight rabbit bucks were pooled and then diluted in INRA-82 supplemented either with (0.5, 1.0 or 1.5 mM) or without (0.0 mM) melatonin. Diluted semen was cooled at 5°C for 24 hr. For cryopreservation and based on the first experiment's best result, semen samples were diluted in INRA-82 in the presence or absence of 1.0 mM melatonin and then frozen in 0.25 ml straws. Following cooling or thawing, sperm quality and DNA integrity were evaluated. Furthermore, the fertility of frozen/thawed semen was investigated after artificial insemination. Supplementation of semen extender with 1.0 mM melatonin improved (p < .05) motility, viability, membrane and acrosome integrities in cooled semen compared with other groups. Sperm quality and DNA integrity were higher (p < .05) in frozen/thawed semen diluted in 1.0 mM melatonin-supplemented extender than in the control group. Conception and birth rates were higher in does inseminated with 1.0 mM melatonin treated semen compared with the controls. In conclusion, supplementation of semen extender with 1.0 mM melatonin improved the quality of cooled and frozen/thawed rabbit spermatozoa. Melatonin can preserve DNA integrity and enhance the fertility of frozen/thawed rabbit spermatozoa.

Cryoprotective Effect of Vitamin E Supplementation of Different Extenders on Quality and Fertilizing Ability of Frozen-Thawed Brown Trout Sperm

Vitamin E is one of the most powerful antioxidants for prevention of cell damage resulting from cryopreservation, but its efficacy for cryopreserving brown trout sperm is still unclear. In this work, the protective effect of vitamin E on quality, fertilizing capacity, and DNA damage of brown trout (Salmo trutta macrostigma) sperm after cryopreservation was evaluated. Sperm samples were diluted at the ratio of 1:10 with three different extenders (E): (E-I): 300 mM glucose, 10% egg yolk; (E-II): 33.3 mM glucose, 5.1 mM NaCl, 0.5 mM NaHCO_3,, 15% DMA; and (E-III): 61.6 mM NaCl, 134.2 mM KCl, 1.9 mM CaCl₂, 0.8 mM MgCl₂, 2.3 mM NaHCO₃ in distilled water. Each extender was supplemented with 10% DMSO and different concentrations of vitamin E at 0.1, 0.5, and 1.0 mM. Spermatozoa frozen without vitamin E (0 mM, control) and fresh sperm were also used. After dilution, the sperm was aspirated into 0.25 mL straws, frozen 3 cm above the liquid nitrogen (LN₂) surface, and plunged into the LN₂. Cell motility, viability, fertilization, and eyeing were determined in post-thawed samples. DNA damage was determined by the comet assay after cryopreservation. Supplementation of 1 mM vitamin E to all extenders exhibited the best cryoprotective effect in terms of sperm motility, duration of motility, viability, fertility, and DNA integrity against cryopreservation damage, compared with 0.1, 0.5, and control group (0 mM) (p < 0.05). The highest post-thaw motility (62.4% ± 0.36%), fertilization (48.2 ± 0.84), and the lowest DNA damage (7.245%) were obtained with the extender-II including 1.0 mM vitamin E (p < 0.05). Consequently, vitamin E positively affected the motility parameters, fertility, and DNA integrity, and the results suggest the addition of extenders with vitamin E as an antioxidant for the cryopreservation of brown trout sperm.

Proline Protects Boar Sperm against Oxidative Stress through Proline Dehydrogenase-Mediated Metabolism and the Amine Structure of Pyrrolidine

Simple Summary

Reactive oxygen species that accumulate during liquid storage of boar semen lead to oxidative stress to sperm. In this study, we found that proline significantly improved boar sperm quality and protected sperm against oxidative damages during liquid storage at 17 °C. Using the model of artificially induced oxidative stress, we found that proline exerted an antioxidative role by modulating redox homeostasis in boar sperm. The secondary amine structure of proline and proline dehydrogenase-mediated metabolism are involved in the antioxidative role. We suggest that addition of proline to the extender would be beneficial to improve boar sperm quality.

Abstract

Proline was reported to improve sperm quality in rams, stallions, cynomolgus monkeys, donkeys, and canines during cryopreservation. However, the underlying mechanism remains unclear. The aim of this study was to investigate the effect of proline on boar semen during liquid storage at 17 °C and explore the underlying mechanism. Freshly ejaculated boar semen was supplemented with different concentrations of proline (0, 25, 50, 75, 100, 125 mM) and stored at 17 °C for nine days. Sperm motility patterns, membrane integrity, ATP (adenosine triphosphate), reactive oxygen species (ROS), and GSH (glutathione) levels, and the activities of catalase (CAT) and superoxide dismutase (SOD) were evaluated after storage for up to five days. It was observed that boar sperm quality gradually decreased with the extension of storage time, while the ROS levels increased. Addition of 75 mM proline not only significantly improved sperm membrane integrity, motility, and ATP levels but also maintained the redox homeostasis via increasing the GSH levels and activities of CAT and SOD. When hydrogen peroxide (H₂O₂) was used to induce oxidative stress, addition of proline significantly improved sperm quality and reduced ROS levels. Moreover, addition of proline also improved sperm quality during the rapid cooling process. Notably, addition of DL-PCA (DL-pipecolinic acid) rescued the reduction of progressive motility and total motility caused by H₂O₂, and THFA (tetrahydro-2-furoic acid) failed to provide protection. Furthermore, addition of proline at 75 mM increased the activity of proline dehydrogenase (PRODH) and attenuated the H₂O₂-induced reduction in progressive motility. These data demonstrate that proline protects sperm against oxidative stress through the secondary amine structure and proline dehydrogenase-mediated metabolism.

Rutin protects boar sperm from cryodamage via enhancing the antioxidative defense

This study was aimed to investigate whether and how Rutin protects boar sperm against cryoinjury during cryopreservation. Five concentrations of Rutin with 0.2, 0.4, 0.6, 1.0, and 2.0 mM were added to the freezing extender of boar sperm, respectively, and the effects on quality and function of boar sperm after freezing-thawing were assessed. The results showed that the sperm motility, mitochondrial activity, plasma membrane integrity, and acrosomal integrity were significantly improved in 0.4 mM and 0.6 mM Rutin groups (p < .05). Compared with ganoderma lucidum polysaccharide (GLP) or Tanshinone IIA, Rutin exhibited higher rates of mitochondrial activity and acrosome integrity (p < .05). Mechanistically, the addition of Rutin at the concentration of 0.6, 0.8, and 1.0 mM significantly attenuated ROS accumulation and MDA production by improving antioxidant enzymatic activity, including SOD, CAT, and GSH-Px (p < .05). Functionally, a higher penetration rate and the increased total efficiency of fertilization were observed in the 0.4, 0.6, and 1.0 mM Rutin groups than in the control group (p < .05). Moreover, the addition of Rutin (0.6 mM) significantly induced an increase in both the cleavage and blastocyst rates (p < .05). In summary, supplementation with Rutin in cryopreservation medium protects boar sperm against ROS attack by enhancing the antioxidative defense.

Improving the Rabbit Semen Cryopreservation Protocol: Comparison Between Two Extenders and Inseminating Doses

This study has been designed to optimize the semen freezing protocol in rabbits, in this regard we compared a Tris-citrate-glucose (TCG) extender with a commercial one (Cortalap®), that to the best of our knowledge has never been used up to now on the in vitro freezability and fertilizing ability of cryopreserved rabbit semen. Two different inseminating semen doses were considered. Five pooled semen samples were divided into two subsamples and each of them were diluted to a ratio 1:1 (v:v) with a freezing extender composed of TCG or Cortalap® containing 16% of dimethylsulfoxide and 0.1 mol/L of sucrose. The extended semen was filled into 0.25 mL plastic straws and frozen above a liquid nitrogen surface. After thawing (50°C/10 seconds) we determined sperm motility, viability, membrane functionality, acrosome and DNA integrity. Our results showed that the Cortalap® extender significantly improved the in vitro post-thaw sperm quality, in comparison to TCG. When we compared the extenders in vivo, no significant differences in the reproductive performances were observed independently by inseminating doses used. In this study we demonstrated that Cortalap® extender can be used as an alternative to TCG. Thus, the Cortalap® being a ready to use extender, implies a reduction of time, mistakes and microbial contaminations during its preparation. This discovery results as significant because it provides beyond an important contribution to the creation of the first Italian semen cryobank of rabbit breeds and also for livestock rabbit farms based on artificial insemination (AI) program.

Alpha-tocopherol improves sperm quality by regulate intracellular Ca2+ intensity (influx/efflux) of Simmental bull cattle sperm

Background

The effects of α-tocopherol on intracellular Ca²⁺ intensity in semen cryopreservation by regulate intracellular Ca²⁺ intensity have not been reported yet.

Objective

The research was conducted to evaluate the effect of supplementation α- tocopherol into egg yolk skim milk extender on sperm quality and intracellular Ca²⁺ intensity.

Methods

Semen samples were collected and supplemented with respectively 0mM (P0); 0.5mM (P1); 1mM (P2); 1.5mM (P3) and 2mM (P4) α-tocopherol in extender before cryopreservation processes. Post-thawing sperm was evaluated for motility, viability, and abnormality using Phase Contrast Microscope (200x) with eosin-nigrosine staining, and intracellular Ca²⁺ intensity of the best result dose was evaluated using Confocal Laser Scan Microscope (400x) with Fluo-3 Staining.

Results

The results showed there was a significant difference (P≤0.05) in sperm motility and viability between P0; P1 with P2; P3; P4. The Motility and viability between groups P0; P1 and P3; P4 showed no significant difference (P≥0.05), while P2 with P3; P4 showed significant difference (P≤0.05). There was a significant difference (P≤0.05) in sperm abnormality of P0; P1 with P2; P3; P4. The abnormality between P0; P1 and P2; P3 showed no significant difference (P≥0.05), while P2; P3 showed a significant difference with P4 (P≤0.05). The best result in sperm quality was supplementation with 1.5mM α-tocopherol. Ca²⁺ intracellular intensity: 142.76± 21.8 au (P0) and 176.06±61.43 au (P3).

Conclusions

It was concluded that 1.5mM α-tocopherol is the best dose to improve sperm quality by regulating intracellular Ca²⁺ intensity on Simmental bull cattle.

Protective effect of vitamin C and lycopene on the in vitro fertilization capacity of sex-sorted bull sperm by inhibiting the oxidative stress

The fertilization capacity of sex-sorted sperms is seriously decreased, which inhibits its wide application. However, little information is still available about the effect of vitamin C (VC) and lycopene (Lyc) on the fertilization capacity of sex-sorted bull sperm. In this study, the washing medium and fertilization medium of sex-sorted sperm from three bull individuals were supplemented with different concentrations of VC (0, 1 × 10^-3 , 1 × 10^-4 , 1 × 10^-5 , 1 × 10^-6  M) or Lyc (0, 1 × 10^-4 , 1 × 10^-5 , 1 × 10^-6 , 1 × 10^-7 ). After washing twice and incubation for 1.5 hr, the malondialdehyde (MDA) level, phosphatidylserine (PS) translocation, membrane potential (Δψm) and IVF (in vitro fertilization) ability of sex-sorted sperm were investigated. For the sex-sorted sperm of bulls A, B and C, 1 × 10^-3  M VC or 1 × 10^-4  M Lyc treatment significantly decreased their MDA levels and PS translocation and increased their Δψm levels and cleavage rates after IVF. When blastocysts were concerned, 1 × 10^-4  M Lyc significantly improved the blastocyst rates and their IFN-tau expression of bulls A and C. In conclusion, supplementation of 1 × 10^-3  M VC or 1 × 10^-4  M Lyc in washing and fertilization medium contributed greatly to improving the fertilization capacity of sex-sorted bull sperm during IVF procedure.

Effects of k-carrageenan supplementation or in combination with cholesterol-loaded cyclodextrin following freezing-thawing process of rooster spermatozoa

This experimental research purposely seeks to explore the effect of supplementing k-carrageenan (k-CRG) or CLC (cholesterol-loaded cyclodextrins) or the combined effect of k-CRG and CLC as supplements of antioxidants to an extender for rooster semen freezing. A total of 75 neat pooled ejaculates were collected twice a week from twenty-five (25) commercial line arbor acres broiler roosters (30 wks) during the experimental period. In each replicate, semen samples (n= 15, three ejaculates per rooster) were pooled and divided into nine equal aliquots, and each aliquot was diluted with one of the following extender supplemented with k-CRG, CLC, and k-CRG + CLC after which it was subjected to cryopreservation process using the "pellet" method. In study I, the supplementation of extenders with k-CRG was in five equal aliquots as follows; (0.2, 0.4, 0.6, 0.8) mg/mL and control group (k-CRG 0) mg/mL while in Study II, there was a combination of both k-CRG + CLC (0.4 mg/mL + 1.5 mg/mL, respectively), 0.4 mg/mL k-CRG, 1.5 mg/mL CLC and control group. Sperm quality parameters, endogenous antioxidant enzymes, lipid peroxidation (MDA) and ROS were all assessed after the freeze-thaw process. Our findings in study I indicated that at post-thaw, an optimum 0.4 mg/mL k-CRG supplementation in the extender improved semen quality parameters, endogenous enzymes, MDA and ROS in comparison to the control group. Interestingly prior to the freeze-thaw process, it was depicted in study II that combined k-CRG + CLC (0.4 mg/mL+1.5 mg/mL) inclusion in the extender provided maximum protection to sperm quality parameters, endogenous enzymes, MDA and ROS in comparison to 1.5 mg/mL CLC and control group at post-thaw. Besides, there was also a significant difference observed in the extenders supplemented with combined k-CRG + CLC (0.4 mg/mL +1.5 mg/mL) when compared to 0.4 mg/mL k-CRG for semen quality parameters and endogenous antioxidant enzymes (SOD, CAT, and GPx) but no significant difference was observed for MDA and ROS. Also, there was a significant difference observed in the extender supplemented with 1.5 mg/mL CLC when compared to the control group for semen quality parameters, SOD, CAT, and MDA but no significant difference for GPx and ROS at post-thaw. In conclusion, k-CRG at an optimal dosage of 0.4 mg/mL proved effective for improving post-thaw sperm quality but its combined addition k-CRG + CLC at an optimal concentration of (0.4 + 1.5) mg/mL in the extender provided greater protection to the rooster spermatozoa at post-thaw.

Notoginsenoside R1 protects boar sperm during liquid storage at 17°C

Reactive oxygen species (ROS) damage mammalian sperm during liquid storage. Notoginsenoside R1 (NR1) is a compound isolated from the roots of Panax notoginseng; it has powerful ROS-scavenging activities. This work hypothesized that the antioxidant capacity of NR1 could improve boar sperm quality and fertility during liquid storage. During liquid storage at 17°C, the supplementation of semen extender with NR1 (50 μM) significantly improved sperm motility, membrane integrity and acrosome integrity after 5 days of preservation. NR1 treatment also reduced ROS and lipid peroxidation (LPO) levels at day 5 (p <0.05). Higher glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) levels and sperm-zona pellucida binding capacity were observed in the 50 μM NR1 group than those in the control group at day 7 (p <0.05). Importantly, statistical analysis of the fertility of 200 sows indicated that addition of NR1 to the extender improved the fertility parameters of boar spermatozoa during liquid storage at 17°C (p <0.05). These results demonstrate the practical feasibility of using 50 μM NR1 as an antioxidant in boar extender during liquid storage at 17°C, which is beneficial to both spermatozoa quality and fertility.

Resveratrol protects boar sperm in vitro via its antioxidant capacity

The objective of the present study was to elucidate whether resveratrol could facilitate the survival of boar sperm during liquid preservation and fast cooling processes. Boar semen were diluted with Modena extender containing different concentrations of resveratrol. Sperm motility was evaluated by visual estimation. Membrane integrity, acrosome integrity and mitochondrial membrane potentials were measured by SYBR-14/PI, FITC-PNA and JC-1 staining, respectively. Moreover, the levels of reactive oxygen species (ROS), malonaldehyde (MDA) and total antioxidant capacity (T-AOC) were measured using commercial assay kits. B-cell lymphoma protein-2 (BCL2) content was determined by western blotting. During liquid preservation at 17oC, the addition of 50 μM resveratrol to the Modena extender significantly improved sperm motility, membrane integrity, acrosome integrity, and sperm mitochondrial membrane potentials. Similar results were also observed in the 150 μM resveratrol group during the fast cooling process. Furthermore, addition of resveratrol led to a decrease of ROS and MDA, and an increase in the content of T-AOC and BCL2. These observations suggest that addition of resveratrol to Modena extender protects boar sperm against oxidative stress. The optimal concentrations of resveratrol are 50 μM and 150 μM during liquid preservation and fast cooling process, respectively.

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.

Negative effects of ROS generated during linear sperm motility on gene expression and ATP generation in boar sperm mitochondria

Mitochondrial oxidative phosphorylation (OXPHOS) is essential for ATP production to maintain sperm linear motility during migration from the uterus to the oviduct. However, ROS are generated as by-products of OXPHOS, causing stress and damaging the sperm quality. This study aimed to clarify the ROS targets in sperm mitochondria that decrease linear motility and to investigate whether mitochondria-target antioxidants (PQQ and CoQ10) affect mitochondrial activity and sperm motility. Sperm linear motility pattern, ATP production, and mitochondrial activity were decreased with increasing ROS levels during incubation in the low-glucose medium. However, sperm motility patterns and ROS levels were not significantly changed in the high-glucose medium. Moreover, the gene expression system (mt-DNA, mitochondrial transcription factor-A (TFAM) and RNA polymerase (POLRMT)) in sperm mitochondria was damaged during incubation in the low-glucose medium. Interestingly, PQQ treatment increased the mt-DNA stability and decreased the damage to TFAM and POLRMT, which resulted in high expression of mitochondrial genes. Furthermore, the antioxidants increased mitochondrial activity and maintained sperm linear motility under the low glucose condition. These results revealed that both ATP production and the mitochondrial transcription system are damaged with increasing ROS levels in sperm that show a linear motility pattern. Treatment with antioxidants, such as PQQ and CoQ10, is beneficial tool to maintain sperm linear motility.

Effect of supplementing vitamin E analogues on post-thaw semen parameters and fertility in chicken

1. The effect of supplementing water-soluble vitamin E analogues 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (trolox) and butylated hydroxy toluene (BHT) was studied in two separate experiments.2. In the first experiment, trolox was supplemented at 0.2 mM, 0.4 mM and 0.8 mM concentrations along with N-methylacetamide (MA; 12% final concentration) and semen was cryopreserved in 0.5 ml French straws. Different semen parameters and fertility were assessed from post-thaw samples.3. Sperm motility, live sperm, and mitochondrial activity were significantly lower (P < 0.05) in cryopreserved semen. Lipid peroxidation (LPO) was significantly higher (P < 0.05) in cryopreserved semen that was reduced by trolox supplementation. The treatment containing trolox at 0.2 mM concentration produced significantly higher (P < 0.05) fertility compared to unsupplemented cryopreservation treatment.4. In the second experiment, BHT was supplemented at 0.25 mM, 0.5 mM, and 1 mM concentrations along with MA during semen cryopreservation.5. Sperm motility, live sperm and MTT dye reduction test were significantly lower (P < 0.05) in cryopreserved semen. These parameters declined with increasing BHT concentration. Abnormal sperm was significantly higher (P < 0.05) in the BHT supplemented treatments. The sperm chromatin dispersion (SCD) test was significantly higher (P < 0.05) in cryopreserved samples and was highest in samples supplemented with 0.5 mM and 1 mM BHT. The percentage fertility was significantly lower (P < 0.05) in cryopreserved semen and BHT supplementation did not improve fertility.6. In conclusion, trolox supplementation at 0.2 mM concentration during semen cryopreservation improved fertility, whereas BHT supplementation resulted in a decline in post-thaw semen parameters.

Melatonin protects rabbit spermatozoa from cryo-damage via decreasing oxidative stress

Mammalian spermatozoa are highly susceptible to reactive oxygen species (ROS) stress. The aim of the present study was to investigate whether and how melatonin protects rabbit spermatozoa against ROS stress during cryopreservation. Semen was diluted with Tris-citrate-glucose extender in presence of different concentrations of melatonin. It was observed that addition of 0.1 mM melatonin significantly improved spermatozoa motility, membrane integrity, acrosome integrity, mitochondrial membrane potential as well as AMP-activated protein kinase (AMPK) phosphorylation. Meanwhile, the lipid peroxidation (LPO), ROS levels and apoptosis of post-thaw spermatozoa were reduced in presence of melatonin. Interestingly, when fresh spermatozoa were incubated with 100 μM H₂O₂, addition of 0.1 mM melatonin significantly decreased the oxidative damage compared to the H₂O₂ treatment, whereas addition of luzindole, an MT1 receptor inhibitor, decrease the effect of melatonin in spermatozoa. It was observed that the glutathione (GSH) content and activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were significantly increased with addition of melatonin during cryopreservation. In conclusion, addition of melatonin to the freezing extender protects rabbit spermatozoa against ROS attack by enhancing AMPK phosphorylation for increasing the antioxidative defense.

Identification of candidate genes in regulation of spermatogenesis in sheep testis following dietary vitamin E supplementation

Dietary vitamin E supplementation is beneficial to semen quality in different sheep and goat breeds. The aim of this research was to further investigate the effect of vitamin E in sheep on spermatogenesis and its regulatory mechanisms using RNA-seq. Thirty male Hu lambs were randomly divided into three groups. The animals received 0, 200 or 2000 IU/day vitamin E dietary supplementation for 105 days, and its effects were subsequently evaluated. The results indicate vitamin E supplementation increased the number of germ cells in the testes and epididymides. The positive effects were reduced, however, in animals that received 2000 IU/d vitamin E. Using the RNA-seq procedure, there was detection of a number of differentially expressed genes such as NDRG1, FSCN3 and CYP26B1 with these genes being mainly related to the regulation of spermatogenesis. Supplementation with 2000 IU/d vitamin E supplementation resulted in a lesser abundance of skeleton-related transcripts such as TUBB, VIM and different subtypes of collagen, and there was also an effect on the ECM-receptor interaction pathway. These changes appear to be responsible for the lesser beneficial effect of the greater vitamin E concentrations. The results provide a novel insight into the regulation of spermatogenesis by vitamin E at the molecular level, however, for a precise understanding of functions of the affected genes there needs to be further study.

Effect of addition of melatonin on liquid storage of ram semen at 4°C

Adding a certain amount of antioxidants to semen extender has been shown to improve semen quality. The aim of present study was to elucidate whether the supplementation of melatonin to the Tris-based extender (CTR) could enhance the quality of ram spermatozoa during storage at 4°C. Ram semen samples were collected and diluted with CTR extender containing different concentrations (0, 0.05 (M 0.05), 0.1 (M 0.1), 0.2 (M 0.2) or 0.4 (M 0.4) mM) of melatonin. Sperm routine indicators, mitochondrial activity, total antioxidant capacity (T-AOC) and malondialdehyde (MDA) content were analysed in control and melatonin treatment groups. The higher per cent of motility, plasma membrane integrity, mitochondrial activity and T-AOC activity was observed in M 0.05, M 0.1 and M 0.2 groups compared to control group at 5 days of storage (p < 0.05), while lower percentage of MDA content was observed among these groups (p < 0.05). In addition, there were no significant differences in acrosome integrity among the control and M 0.05, M 0.1 and M 0.2 groups during the experiment. The above results show that the addition of 0.05, 0.1, 0.2 mM of melatonin is beneficial to the preservation of ram semen during liquid storage at 4°C mainly through antioxidative stress.

Comparing Human Sperm Quality Preserved at Two Different Temperatures; Effect of Trolox, Coenzyme Q10 and Extracellular Adenosine Triphosphate

Cooling method was proposed to maintain the sperm quality for several days. Nevertheless, during this procedure, sperm is encountered to "cold shock", and its quality decreases time-dependently. This study was designed to improve the in vitro sperm preservation methods. Thirty normal semen samples were examined in Shiraz, Iran, 2017. Fifteen samples were incubated at 22-27 °C and 15 samples were cooled moderately to 4 °C. Each sample was divided into five subgroups; control, solvent, 200 μM Trolox, 40 μM Coenzyme Q10, and 10 mM ATP. ATP was added only 15 minutes before the analysis. Assessments of motility parameters and sperm viability were done every 24 hours. Statistical analysis was performed using SPSS 16 software. The differences between two main groups and subgroups were compared by t test and one-way ANOVA, respectively. The effect of time was analyzed by repeated measurement test. Sperm motility and viability were the same in both groups until 24 hours, except the straight line velocity was greater in the cold group. Even after 48 hours, progressive motility and sperm velocity, but not viability, were still the same. The greatest reduction in progressive motility occurred on the second day; and after 72 hours, sperm quality was better preserved in 22-27 °C. Treatment with Trolox, coenzyme-Q10, and extracellular ATP did not have effect on sperm quality. Cold temperature is recommended for in-vitro sperm preservation up to 24 hours, and 22-27 °C is preferred for longer time storage. The sperm does not need antioxidant therapy for quality maintenance, but the extender media must be supplied with nutrients and antibiotics.

Evaluation of Intracellular Location of Reactive Oxygen Species in Solea Senegalensis Spermatozoa

Oxidative stress is one of the important factors in decreasing sperm quality. Developing efficient protocols for detecting reactive oxygen species (ROS) in spermatozoa is of high importance in any species, but these methods are rarely used and even less in teleost. Cryopreservation is a useful technique in aquaculture for different purposes, including gene banking and guaranteed sperm availability throughout the year. Freezing/thawing procedures could cause ROS production and damage the sperm cells. Considering the prospective damage that an excess of ROS production could cause in spermatozoa depending on their localization, here a detailed methodology to detect H2O2 and to evaluate its intracellular localization by confocal microscopy is provided. For this purpose, a combination of 3 fluorochromes (2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA), a live mitochondria stain and 4',6-Diamidino-2-phenylindole dihydrochloride (DAPI)) are used to evaluate the co-localization of H2O2 with spermatozoa nuclei or mitochondria in Solea senegalesis sperm samples.

A chemical compound based on methylxanthine-polyphenols lowers nitric oxide levels and increases post-thaw human sperm viability

We produced a new chemical compound based on methylxanthines and polyphenols (CCMP) present in the chemical matrix of guaraná (Paullinia cupana), a seed extract with antioxidant properties. After supplementation with the standard extract of resveratrol, a well documented antioxidant found in other plant sources, we investigated whether this resveratrol-enriched compound could improve sperm viability and modulate differentially reactive oxygen species (ROS) and nitric oxide (NO) levels in thawed sperm. Sperm samples obtained from healthy young donors were treated with different concentrations of guaraná extract (0.1, 1, 5 or 10 mg/ml) and cells were frozen at -80°C for 24 h. In addition, the potential protective effects of guaraná treatment on sperm treated with pro-oxidant compound (200 µM hydrogen peroxide, H2O2) were assessed. Samples were also exposed to three concentrations of CCMP before being frozen in liquid nitrogen (-196°C) or in an ultrafreezer (-80°C) for 24 h, and both pre-freezing and post-thaw measurements of viability and oxidative stress were performed. Guaraná supplementation at 10 mg/ml significantly increased post-thaw viability and decreased oxidative metabolism of the sperm. Moreover, selected concentrations of CCMP improved viability and oxidative metabolism in sperm samples pre-freezing. Furthermore, CCMP showed cryoprotective activity by increasing viability and decreasing oxidative stress in post-thaw samples. In summary, these findings suggested that CCMP supplementation acts as a cryoprotectant to modulate ROS and NO levels in thawed sperm. CCMP could be used to enhance sperm quality and reproductive success.

Reactive oxygen species as mediators of sperm capacitation and pathological damage

Oxidative stress plays a major role in the life and death of mammalian spermatozoa. These gametes are professional generators of reactive oxygen species (ROS), which appear to derive from three potential sources: sperm mitochondria, cytosolic L-amino acid oxidases, and plasma membrane Nicotinamide adenine dinucleotide phosphate oxidases. The oxidative stress created via these sources appears to play a significant role in driving the physiological changes associated with sperm capacitation through the stimulation of a cyclic adenosine monophosphate/Protein kinase A phosphorylation cascade, including the activation of Extracellular signal regulated kinase-like proteins, massive up-regulation of tyrosine phosphorylation in the sperm tail, as well as the induction of sterol oxidation. When generated in excess, however, ROS can induce lipid peroxidation that, in turn, disrupts membrane characteristics that are critical for the maintenance of sperm function, including the capacity to fertilize an egg. Furthermore, the lipid aldehydes generated as a consequence of lipid peroxidation bind to proteins in the mitochondrial electron transport chain, triggering yet more ROS generation in a self-perpetuating cycle. The high levels of oxidative stress created as a result of this process ultimately damage the DNA in the sperm nucleus; indeed, DNA damage in the male germ line appears to be predominantly induced oxidatively, reflecting the vulnerability of these cells to such stress. Extensive evaluation of antioxidants that protect the spermatozoa against oxidative stress while permitting the normal reduction-oxidation regulation of sperm capacitation is therefore currently being undertaken, and has already proven efficacious in animal models.

Cysteine protects rabbit spermatozoa against reactive oxygen species-induced damages

The process of cryopreservation results in over-production of reactive oxygen species, which is extremely detrimental to spermatozoa. The aim of this study was to investigate whether addition of cysteine to freezing extender would facilitate the cryosurvival of rabbit spermatozoa, and if so, how cysteine protects spermatozoa from cryodamages. Freshly ejaculated semen was diluted with Tris-citrate-glucose extender supplemented with different concentrations of cysteine. The motility, intact acrosomes, membrane integrity, mitochondrial potentials, 8-hydroxyguanosine level and sperm-zona pellucida binding capacity were examined. Furthermore, glutathione peroxidase (GPx) activity, glutathione content (GSH), and level of reactive oxygen species (ROS) and hydrogen peroxide of spermatozoa were analyzed. The values of motility, intact acrosomes, membrane integrity, mitochondrial potentials and sperm-zona pellucida binding capacity of the frozen-thawed spermatozoa in the treatment of cysteine were significantly higher than those of the control. Addition of cysteine to extenders improved the GPx activity and GSH content of spermatozoa, while lowered the ROS, DNA oxidative alterations and lipid peroxidation level, which makes spermatozoa avoid ROS to attack DNA, the plasma membrane and mitochondria. In conclusion, cysteine protects spermatozoa against ROS-induced damages during cryopreservation and post-thaw incubation. Addition of cysteine is recommended to facilitate the improvement of semen preservation for the rabbit breeding industry.