Antioxidative effects of magnetized extender containing bovine serum albumin on sperm oxidative stress during long-term liquid preservation of boar semen

Effect of Magnetized Freezing Extender on Membrane Damages, Motility, and Fertility of Boar Sperm Following Cryopreservation

Magnetized water is defined as the amount of water that has passed through a magnet. The magnetic field weakens the hydrogen bonds between the water molecules, leading to the magnetized liquid acquiring special characteristics such as easy supercooling and forming smaller ice crystals. We researched the influences of a magnetized freezing extender on cell membrane damage and in vitro fertilization of boar sperm during cryopreservation. The freezing extenders were passed through 0, 2000, 4000, and 6000 gausses (G) of magnetic devices using a liquid cycling pump system and then used for the sperm freezing process. The damage to plasma, acrosomal, and mitochondrial membranes in frozen-thawed spermatozoa was investigated by flow cytometry, and motility was assessed using the CASA system. The fertility of frozen-thawed sperm was estimated using in vitro fertilization. The damage to the membranes was significantly decreased in the magnetized freezing extender by the 6000 G magnetic field compared to that of the control in frozen-thawed sperm, and motility was increased in the 6000 G group. Although there were no significant differences in the cleavage rates of in vitro fertilized oocytes among the treatment groups, the ratio of blastocyst formation increased in the magnetized freezing extender groups compared with that in the control group. The number of blastocysts was significantly higher in the 4000 G group than in the 0 G group. In conclusion, these results suggest that a magnetized freezing extender could improve the freezability of sperm and the development of oocytes fertilized in vitro with frozen-thawed sperm.

Hydroxytyrosol effectively improves the quality of pig sperm at 17 °C

Artificial insemination (AI) is a proven breeding technology which has been widely used in pig reproduction. Low temperature can cause very serious damage to pig sperm below 15 °C and the situation is even more serious at lower temperature. Besides, the preservation of pig sperm is mainly carried out at 17 °C because of its outstanding performance in pig reproduction. However, the accumulation of a large amount of reactive oxygen species (ROS) during the preservation process is the main reason for the deterioration of sperm quality. In our research, by adding different concentrations of hydroxytyrosol to the diluent during the storage of pig sperm at 17 °C, we compared them with the traditional diluent to study the sperm motility, the cumulative amount of ROS, the extent of sperm membrane damage, the sperm acrosome integrity, the sperm DNA damage and the activity of antioxidant enzymes (CAT, T-AOC, SOD, GSH-PX, MDA) to evaluate the effect of hydroxytyrosol on the sperm quality during storage. We used proteomics sequencing technology to monitor difference in sperm protein between the control samples and the addition of 120 μmol/L hydroxytyrosol samples (optimum concentration) after three days storage. Ultimately, we selected the control samples and the addition of 120 μmol/L hydroxytyrosol samples to test the effect of AI. The results of our research showed that during storage of pig sperm at 17 °C, the sperm quality and antioxidant capacity of the hydroxytyrosol-treated samples significantly improved (HT 120 μmol/L) (P < 0.05). Proteomics sequencing analysis proved that the addition of 120 μmol/L hydroxytyrosol treatment samples had potential value in improving sperm quality. The significant increase in sow pregnancy rate and piglet birth weight proved that hydroxytyrosol had important practical value in pig reproduction. Based on our results, we demonstrated that the addition of hydroxytyrosol to the diluent could improve the quality of pig sperm and the efficiency of AI.

Exogenous Albumin Is Crucial for Pig Sperm to Elicit In Vitro Capacitation Whereas Bicarbonate Only Modulates Its Efficiency

Simple Summary

In this work, we addressed if the presence of exogenous bicarbonate required for pig sperm capacitation, which is a necessary step to acquire fertilizing ability. While sperm incubated in media without BSA or BSA/bicarbonate did not achieve in vitro capacitation, those incubated with BSA reached that status under any bicarbonate concentration, even when bicarbonate was absent. Interestingly, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and higher concentration of bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed lower motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is crucial in for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. In contrast, although exogenous bicarbonate does not appear to be indispensable, it shortens the time needed to reach that capacitated status.

Abstract

This work sought to address whether the presence of exogenous bicarbonate is required for pig sperm to elicit in vitro capacitation and further progesterone-induced acrosome exocytosis. For this purpose, sperm were either incubated in a standard in vitro capacitation medium or a similar medium with different concentrations of bicarbonate (either 0 mM, 5 mM, 15 mM or 38 mM) and BSA (either 0 mg/mL or 5 mg/mL). The achievement of in vitro capacitation and progesterone-induced acrosomal exocytosis was tested through the analysis of sperm motility, plasma membrane integrity and lipid disorder, acrosome exocytosis, intracellular calcium levels, mitochondria membrane potential, O₂ consumption rate and the activities of both glycogen synthase kinase 3 alpha (GSK3α) and protein kinase A (PKA). While sperm incubated in media without BSA or BSA/bicarbonate, they did not achieve in vitro capacitation; those incubated in media with BSA achieved the capacitated status under any bicarbonate concentration, even when bicarbonate was absent. Moreover, there were differences related to the concentration of bicarbonate, since sperm incubated in media with BSA and with no bicarbonate or 5 mM bicarbonate showed lower overall efficiency in achieving in vitro capacitation than those incubated in the presence of BSA and 15 mM or 38 mM bicarbonate. Additionally, at the end of the experiment, sperm incubated in the presence of BSA and 38 mM bicarbonate showed significantly (p < 0.05) lower values of motility and plasma membrane integrity than those incubated in media with BSA and lower concentrations of bicarbonate. In conclusion, BSA is instrumental for pig sperm to elicit in vitro capacitation and trigger the subsequent progesterone-induced acrosome exocytosis. Furthermore, while exogenous bicarbonate does not seem to be essential to launch sperm capacitation, it does modulate its efficiency.

Protective effect of L-carnitine on apoptosis, DNA fragmentation, membrane integrity and Lipid peroxidation of spermatozoa in the asthenoteratospermic men

This in vitro study aimed to measure the ameliorative effect of L-carnitine against apoptosis, DNA fragmentation, membrane integrity and lipid peroxidation of spermatozoa from men with asthenoteratozoospermia (ATS). L-carnitine has an impressive effect on boosting the quality and quantity of spermatozoa and also can prevent apoptosis induction. For this purpose, semen samples were collected from 50 ATS men. Semen was divided into control and L-carnitine (0.5 mg/ml) groups at 2, 4, 6 and 24 hr. Concentrating on the reasons for apoptosis is an arduous process, but in the present research for this evaluation, mitochondrial membrane potential (MMP), DNA fragmentation by TUNEL and SCD methods, and lipid peroxidation were carried out. Also, sperm viability was performed. In the control group, MDA levels were increased significantly at 6 hr; however, sperm viability was decreased significantly at 4 and 6 hr. Moreover, in the L-carnitine group, TUNEL, SCD and MDA levels were decreased significantly and MMP and viability were increased significantly compared with the control group. In this writers' view, in vitro L-carnitine treatment can downregulate apoptosis in men with ATS.

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.

Electromagnetic field in human sperm cryopreservation improves fertilizing potential of thawed sperm through physicochemical modification of water molecules in freezing medium

Physicochemical properties of water molecules as the main compositions of the freezing media can be affected by the electromagnetic fled. The purpose of this study was to apply extremely low repetition rate electromagnetic fields (ELEFs) to change the molecular network of water molecules existing in freezing media used for human sperm cryopreservation. First, different time periods and pulsed electromagnetic fields were used to evaluate the physiochemical properties of water. The lowest rate of cluster size, surface tension, viscosity, and density was observed for water samples exposed to 1000 Hz ELEF for 60 min (P < 0.05) that could be results in small ice crystal formation. Therefore, this treatment was selected for further evaluations in human sperm freezing because there was minimal probability of amorphous ice crystallization in this group. To assess fertilizing potential, human semen samples were subjected to ELEF (1000 Hz) water-made freezing medium and cryopreserved. The highest percentage of total motility, progressive motility, viability, membrane integrity, mitochondrial membrane potential, DNA integrity, and TAC were obtained in frozen ELEF as compared to other groups. The percentage of viable spermatozoa (Annexin V-/PI-) in frozen ELEF was significantly higher than in frozen control. The level of ROS was significantly lower in frozen ELEF when compared to frozen control. It can be concluded that the modification of physicochemical properties of water existing in cryopreservation media by ELEF is a suitable strategy to improve the outcome of cryopreservation.

Sperm quality characteristics and fertilization capacity after cryopreservation of rooster semen in extender exposed to a magnetic field

There has not been as much success in the effectiveness of avian semen cryopreservation as that of mammalian semen cryopreservation. This has been attributed to the unique characteristics of poultry sperm. In the area of mammalian semen, the use of magnetized extenders has enhanced the cryo-resistance of sperm in some species. The applicability of this strategy to avian semen has not yet been evaluated. The purpose of this study was to evaluate the effects on sperm quality and fertility after magnetization of extenders and use of these extenders for cryopreservation of rooster semen. Extenders were passed between two neodymium magnets that produced different magnetic induction values (0, 2000, 4000 and 6000 G). Physicochemical properties of the extenders were assessed and then semen samples were cryopreserved in the magnetized extenders. The smallest cluster sizes and zeta potentials in the extenders were observed in the extender magnetized at 2000 gauss (G). There were greater percentages of sperm total motility, viability and mitochondrial membrane potential in semen treated with the extender magnetized at 2000 G A greater percentage of sperm with enhanced membrane functionality was observed when sperm were stored in extenders magnetized with 2000 G and 4000 G. In a field trial, there were greater percentages of fertility and hatching rates of eggs using semen treated with extenders magnetized at 2000 G and 4000 G. Cryopreservation of rooster semen with magnetized extenders at 2000-4000 G resulted in enhanced quality indices of thawed sperm as well as the fertility capacity of the cryopreserved semen.

A mechanism by which Astragalus polysaccharide protects against ROS toxicity through inhibiting the protein dephosphorylation of boar sperm preserved at 4 °C

Numerous studies have shown that Astragalus polysaccharide (APS) has strong antioxidant effects and high practical value for preserving semen at low temperatures in vitro. However, to date, little attention has been paid to the precise mechanism of APS in sperm preservation at 4 °C. Thus, to gain further insight into the protective effects of APS, the present study was performed to assess the changes in sperm quality parameters, antioxidant capacity, ATP content, and protein phosphorylation levels. Here, we demonstrated that supplementation with APS could effectively preserve boar sperm quality parameters such as sperm motility, acrosome integrity, and mitochondrial membrane potential. Moreover, we found that the positive effects of APS on boar sperm quality were mainly due to the elimination of excessive mitochondrial ROS, the improvement of antioxidant capacities and the enhancement of ATP levels. Interestingly, by conducting a series of studies on protein phosphorylation, we also discovered that APS could protect boar sperm from oxidative stress and energy deficiency through inhibiting the protein dephosphorylation caused by ROS via the cAMP-PKA signaling pathway. To our knowledge, this is the first exploration of the molecular mechanism underlying the protective roles of APS toward ROS toxicity from the perspective of energy metabolism and protein modification. This study comprehensively provides novel insights into the action mechanism of the protective effects of antioxidants on sperm stored at 4 °C and reveals the practical feasibility of using APS as a boar semen extender supplement for assisted reproductive technology.

Boar management and semen handling factors affect the quality of boar extended semen

Artificial insemination (AI) is the preferred method for reproduction in the majority of the intensive pig production systems Worldwide. To this end, fresh extended ready-to-use semen doses are either purchased from AI-centres or produced by boars kept on-farm. For profitable semen production, it is necessary to obtain a maximum amount of high quality semen from each boar. This paper reviews current knowledge on factors that may affect semen quality by influencing the boar or the semen during processing. Genetic markers could be used for early detection of boars with the highest fertility potential. Genetic selection for fast growth might jeopardize semen quality. Early detection of boars no longer fit for semen production might be possible by ultrasonography of the testes. Seasonal variation in sperm quality could be associated with changes in photoperiod and heat stress during summer. Comfortable housing, with appropiate bedding material to avoid locomotion problems is essential. In some areas, cooling systems may be necessary to avoid heat stress. The sperm quality can be manipulated by feeding strategies aiming, for instance, to increase sperm resistance to oxidative stress and extend storage duration. High collection frequency will negatively influence sperm quality. Also, if collection is not hygienically performed it will result in bacterial contamination of the semen doses. The concern over bacterial contamination has risen not only because of its negative effect on semen quality but also due to the detection of antimicrobial resistance in isolates from extended semen. Moreover, bacterial and viral pathogens must be monitored because they affect semen production and quality and constitute a risk of herd infection. During processing, boar sperm are submitted to many stress factors that can cause oxidative stress and capacitation-like changes potentially reducing their fertility potential. Dilution rate or dilution temperature affects the quality of the semen doses. Some packaging might preserve semen better than others and some plastic components might be toxic for sperm. Standard operation procedures and quality assurance systems in AI centres are needed.

Development of In Vitro Embryo Production System Using Collagen Matrix Gel Attached with Vascular Endothelial Growth Factor Derived from Interleukin-1 Beta-Treated Porcine Endometrial Tissue

The aim of this study was to establish an embryo culture system using collagen gel attached with vascular endothelial growth factor (VEGF) derived from interleukin-1 beta (IL-1β)-treated endometrial tissues from pigs. Endometria were separated from the porcine uterus at the follicular phase of the estrous cycle and were cultured with IL-1β. The collagen gels coincubated with IL-1β-treated endometria (C, without endometrial tissue; CE, with endometrial tissue; and CEI, IL-1β-treated endometrial tissue) were used for embryo culture. We found that, compared with the comparable figures in the control group, prostaglandin synthase-2 (PTGS-2) mRNA was increased in IL-1β-treated endometrial tissue (p < 0.05). The VEGF protein was not observed in collagen gel coincubated without endometrial tissue (C); however, it was detected in collagen gels coincubated with endometrial tissue (CE and CEI). The embryo cleavage rates and blastocyst formation did not differ among the treatment groups. The proportion of blastocysts did not differ among the groups. However, the number of blastocyst cells was significantly (p < 0.05) higher in the CEI group than in the other groups. These results clarify the effects of the intrauterine environment on preimplantation embryos and may be useful in research on the effects of extracellular matrix- and cytokine-treated endometrial tissue on embryo development.