Absence of beneficial effects on rabbit sperm cell cryopreservation by several antioxidant agents

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.

Extender Supplementation with Glutathione (GSH) and Taurine Improves In Vitro Sperm Quality and Antioxidant Status of New Zealand Rabbits during Chilled Storage for up to 72 hours

This study assessed the influence of supplementing the rabbit semen extender with various concentrations of glutathione (GSH) and taurine at 24, 48, and 72 h postchilling at 5°C. Semen samples were collected from 20 New Zealand bucks, and ejaculates with standard color, motility (>85%), about 0.5 mL volume, and ∼400 × 106/mL concentration were used and diluted with extenders supplemented with 0.5, 1, and 2 mM of GSH and 1, 5, and 10 mM of taurine and chilled at 5°C. Nonsupplemented samples were used as a control. Sperm's progressive motility, acrosome reaction, and extracellular oxidative stress biomarkers such as MDA contents and GPx, SOD, and CAT concentrations and intracellular transcriptomic levels of SOD and CAT genes were assessed. GSH and taurine supplementation improved the sperm's kinetics by reducing cooling-associated stress, which was ascertained by lowering MDA concentration and increasing SOD, CAT, and GPx concentrations (P < 0.05). Increasing the levels of antioxidant enzymes in the extender was due to the increasing mRNA copies of the SOD and CAT genes (P < 0.05). Furthermore, GSH and taurine maintained the fructose levels in the extender and lowered the GPT levels, which implies sperm membrane stability is maintained through GSH and taurine supplementation. GSH and taurine supplementation to the extender had protective influences on the in vitro rabbit semen quality during chilled storage for up to 72 h, which were remarkable with increasing supplementation dose and cooling time at 5°C.

Effect of Honey, Coenzyme Q10, and β-Carotene/α-Tocopherol as Novel Additives in Rabbit-Sperm Cryopreservation Extender

The effectiveness of rabbit-sperm cryopreservation is still below average compared to other domestic species. After the sperm cryopreservation process, post-thawing parameters like motility and membrane integrity are significantly compromised. The use of new extender constituents is an approach that can be used to improve the effectiveness of cryopreservation. Accordingly, we used honey (1.25, 2.5, 5, and 10%), coenzyme Q10 (100 and 200 μM), and β-carotene/α-tocopherol (500 μM/620 μM and 250 μM/310 μM) as candidate components for rabbit-sperm extenders during cryopreservation. Ejaculates from commercial adult rabbit bucks (n = 5) were cryopreserved using conventional freezing. Several post-thawing sperm parameters were assessed, including total motility, membrane integrity, viability, nuclear membrane integrity, acrosome reaction, and mitochondrial membrane potential and activation. Additionally, we performed hormonal analyses of the seminal plasma. Moreover, we analyzed the post-thawing levels of a molecular marker of sperm quality, proAKAP4, which was used in rabbits for the first time. Our findings showed that the 2.5% honey supplementation increased the post-thawing sperm motility (13.75 ± 3.75%) compared to the greater concentrations employed. However, the post-thawing motility was negatively affected by the coenzyme Q10 (0%, in both groups) but was not affected by the β-carotene/α-tocopherol supplementation (22 ± 18.15%, and 11.67 ± 10.17%). In conclusion, the cryopreservation protocols of this study did not help to maintain the sperm parameters after thawing. Further studies are required to identify novel protocols to mitigate the damage caused to rabbit sperm during cryopreservation.

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.

Glutathione supplementation in semen extender improves rabbit sperm attributes during refrigeration

In the present study, we evaluated the sustaining effect of various glutathione (GSH) concentrations in extender on rabbit sperm attributes during storage at 5°C for 24 h. Semen was collected from regular donor rabbit bucks using an artificial vagina and initially evaluated for sperm quality. The qualifying ejaculates were diluted with one of the extenders having 0, 1, 2, 4 or 8 mM GSH, to achieve a final concentration of 1×108 sperm/mL. The extended samples were stored at 5°C for 24 h. Sperm motility, motion kinetics, acrosome integrity and viability were assessed after 3, 6, 12 and 24 h of storage. The results showed that total sperm motility and sperm motion kinetics (oscillation index of the sperm, straightness index and beat cross frequency) were influenced (<em>P</em>&lt;0.05) by glutathione dose and refrigeration time. An interaction of (<em>P</em>&lt;0.05) GSH concentrations and refrigeration time was observed for sperm viability and acrosome reaction rate. In conclusion, the 4 mM GSH supplemented extender’s protective influence was remarkable to maintainrabbit sperm quality for 24 h 5°C.

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.

The Antibacterial and Antioxidant Roles of Buckwheat Honey (BH) in Liquid Preservation of Boar Semen

In the present study, we hypothesized that buckwheat honey (BH) should be regarded as a potential alternative to antibacterial and antioxidant agent in liquid storage of boar semen. To this end, boar semen was firstly studied for in vitro dose tolerability to BH by measuring sperm progressive motility. The optimum progressive motility of boar spermatozoa was observed in extender with 0.5% and 0.6% BH addition. Afterward, sperm quality parameters, bacterial profile and composition, total antioxidant (T-AOC), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels of control, BH supplementation, antibiotics supplementation, and incorporated supplementation were compared during liquid storage period, to further investigate antibacterial and antioxidant properties of BH. The results showed that BH supplementation significantly improved sperm motility, acrosome integrity, plasma membrane integrity, inhibited opportunistic bacterial growth, and altered microbial compositions at the end of preservation. Additionally, T-AOC, SOD, and CAT levels were significantly higher in the BH supplementation group than those in the control and antibiotic supplementation group, whereas MDA level exhibited opposite change pattern. Importantly, BH addition to the extender was able to exert a synergistic effect in combination of antibiotic use. Our findings suggested that the appropriate concentrations (0.5% and 0.6%) of BH were added to the extender could act antibacterial and antioxidant roles in liquid preservation of boar semen.

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.

Antioxidant Effect of a Polyphenol-Rich Murtilla (Ugni molinae Turcz.) Extract and Its Effect on the Regulation of Metabolism in Refrigerated Boar Sperm

The production of reactive oxygen species (ROS) in boar spermatozoa increases in refrigeration; this can have an impact on sperm quality and fertilization capacity. We evaluated the effect of polyphenol-rich aqueous extract of murtilla (Ugni molinae Turcz) on boar sperm stored at 17°C in order to reduce oxidative stress and improve sperm quality in the long term. Five experiments were performed: first, characterization of the polyphenol content from five genotypes of murtilla; second, determination of the genotype with the best antioxidant effect (MT-Ex); third, the antioxidant capacity on O₂⁻ and lipid peroxidation; fourth, the influence of MT-Ex on motility, calcium movement, cAMP, and metabolic parameters; and fifth, analysis of long-term refrigeration. The average phenolic content was 344 ppm; gallic acid, catechin, quercetin, myricetin, and kaempferol were detected. All extracts evaluated presented a concentration-dependent antioxidant effect. MT-Ex reduces intracellular O₂⁻/peroxides but low lipid peroxidation. MT-Ex in nonstimulated ROS conditions reduces sperm motility, mitochondrial membrane potential, cAMP, and ATP, but the succinate dehydrogenase activity remained normal; also, we observed a reduction in calcium movement in in vitro sperm capacitation. The long-term analyses showed that MT-Ex improved sperm motility decay and reduced membrane damage and ROS at 168 h. Based on this study, we propose MT-Ex as a supplement in semen extenders.

BMP2, 4 and 6 and BMPR1B are altered from early stages of bovine cystic ovarian disease development

Cystic ovarian disease (COD) is an important cause of subfertility in dairy cattle. Bone morphogenetic proteins (BMPs), mainly BMP2, BMP4 and BMP6, play a key role in female fertility. In this study, we hypothesized that an altered BMP system is associated with ovarian alterations contributing to COD pathogenesis. Therefore, we examined the expression of BMP2, BMP4 and BMP6 and BMP receptor 1B (BMPR1B) in the ovaries of animals with spontaneous or ACTH-induced COD, as well as during the development of the disease, in a model of follicular persistence induced by low doses of progesterone (at 5, 10 and 15 days of follicular persistence). Results showed changes in BMP2, BMP4 and BMP6 expression during folliculogenesis, in granulosa and theca cells in the COD groups, as well as at different stages of follicular persistence. Results also showed changes in BMPR1B expression in developing follicles in animals with COD, and at the initial stages of follicular persistence (P5). Comparison between groups showed significant differences, mainly in BMP4 and BMP6 expression, in granulosa and theca cells of different follicular categories. The expression of these BMPs also increased in cystic and persistent follicles, in relation to antral follicles of the control group. BMPR1B showed high expression in cystic follicles. Together, these results may indicate an alteration in BMPs, especially in BMP4 and BMP6, as well as in BMPR1B, which occurs early in folliculogenesis and incipiently during the development of COD, which could be a major cause of recurrence of this disease in cattle.

Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/152/4/333.abstract.