Validation of Calcein Violet as a New Marker of Semen Membrane Integrity in Domestic Animals

Many fluorochromes routinely used in semen quality analysis emit in the green and red channels, limiting their possible combination for multiple parameter analysis. The use of fluorophores emitting in different light channels broadens the possibilities of combination to expand the range of simultaneously evaluated criteria. This is of great interest in cases of small ejaculated volumes, such as those naturally occurring in roosters, small dog breeds and drones (Apis mellifera). The purpose of this experiment is to establish Calcein Violet (CaV), a blue fluorochrome, as a marker of viability and acrosomal integrity in domestic animals in order to free the red and green channels. SYBR®14/Propidium Iodide (PI) was used as reference dye, heat-treated samples as negative controls, serial staining combination for validation and epifluorescence microscopy for observation. Dead spermatozoa marked in red with PI showed no blue fluorescence either from the head or the tail. Live spermatozoa showed a decreasing blue emission from head to tail when single stained with CaV. Unreacted acrosomes showed intense blue fluorescence irrespective of plasma membrane integrity. This needs to be further confirmed for species with small and difficult to observe heads. Establishment of CaV as a marker of membrane integrity by fluorescence microscopy is a decisive first step towards further technical development and use with flow cytometry.

Epicatechin Prevents Cryocapacitation of Bovine Spermatozoa through Antioxidant Activity and Stabilization of Transmembrane Ion Channels

Epicatechin (EPC) is a flavonoid belonging to the family of catechins; it has been described as a powerful scavenger of a wide spectrum of reactive oxygen species (ROS) and a modulator of ex vivo sperm vitality. In this study, we assessed the potential protective abilities of EPC on cryopreserved bovine spermatozoa. We focused on conventional quality parameters, as well as the oxidative profile of spermatozoa alongside capacitation patterns, and expression profiles of proteins involved in the process of capacitation. Semen samples were cryopreserved in the presence of 25, 50 or 100 μmol/L EPC and compared to native semen (negative control) as well as ejaculates frozen in the absence of EPC (positive control). A dose-dependent improvement of conventional sperm quality parameters was observed following EPC administration, particularly in case of the sperm motility, membrane, acrosome and DNA integrity in comparison to the positive control. Experimental groups exposed to all EPC doses presented with a significantly lower proportion of capacitated spermatozoa as opposed to the positive control. While no significant effects of EPC were observed in cases of superoxide production, a significant decrease in the levels of hydrogen peroxide and hydroxyl radical were recorded particularly in the experimental groups supplemented with 50 and 100 μmol/L EPC. Western blot analysis revealed that supplementation of particularly 100 μmol/L EPC to the semen extender prevented the loss of the cation channel of sperm (CatSper) isoforms 1 and 2, sodium bicarbonate cotransporter (NBC) and protein kinase A (PKA), which play important roles in the process of sperm capacitation. In summary, we may hypothesize that EPC is particularly effective in the stabilization of the sperm membrane during the freeze-thaw process through its ability to quench ROS involved in damage to the membrane lipids and to prevent the loss of membrane channels crucial to initiate the process of sperm capacitation. These attributes of EPC provide an additional layer of protection to spermatozoa exposed to low temperatures, which may be translated into a higher post-thaw structural integrity and functional activity of male gametes.

In vitro versus cryo-induced capacitation of bovine spermatozoa, part 1: Structural, functional, and oxidative similarities and differences

Low temperatures during cryopreservation activate a cascade of changes, which may lead into irreversible damage and reduction of the fertilization potential, including the process of premature capacitation. The aim of our study was to evaluate the range of cell damage following the cryopreservation process and possible activation of cryocapacitation in bovine spermatozoa. For the experiments semen samples were obtained from 30 sexually mature Holstein bulls. Within the analysed parameters, we focused on the functional activity, structural integrity, capacitation status and oxidative profile. The samples were divided into three experimental groups, control (CTRL), in vitro capacitated (CAP) and cryopreserved (CRYO). Based on the collected data, there was a significant decrease in the sperm motility, mitochondrial membrane potential and concentration of cyclic adenosine monophosphate in the CRYO group when compared to CAP and CTRL (P<0.0001). A significant decrease (P<0.01; P<0.0001) in the membrane and acrosome integrity as well as DNA fragmentation index and a significant increase (P<0.0001) of necrotic cells were observed in the CRYO group. Following capacitation, a significant increase (P<0.01; P<0.0001) was recorded in the number of cells which underwent the acrosome reaction in the CRYO group against CAP and CTRL. Changes in the oxidative profile of the CRYO group indicates an increase (P<0.0001) in the reactive oxygen species generation, except for the superoxide radical, which was significantly higher (P<0.0001; P<0.001) in the CAP group in comparison with CRYO and CTRL. In summary, premature capacitation may be considered a consequence of cryopreservation and the assessed parameters could serve as physical markers of cryogenic damage to bovine spermatozoa in the future.

Effect of Milk Type Subjected to Different Heat Treatments on Cryo-Survivability and In Vivo Fertility of Buffalo (Bubalus bubalis) Spermatozoa in a Milk-Based Extender

Oxidative stress is a major contributory factor to cellular damage during semen cryopreservation and results in a decreased fertilizing capacity of cryopreserved bull sperm. The inclusion of exogenous antioxidants sometimes exerts deleterious effects on sperm quality. Thus, enhancing the endogenous production of antioxidants is a requirement. This study aimed to investigate the effect of milk type heated at different temperatures on the antioxidant potential of extenders, and the subsequent post-thaw quality parameters and in vivo fertility of buffalo bull semen. Cow (C) and buffalo whole milk (B) were used separately for semen extender preparation, heated at five different temperatures (T₁ = 90°C, T₂ = 100°C, T₃ = 110°C, T₄ = 120°C, T₅ = 130°C) for 10 minutes. Reactive sulfhydryl groups were measured in each subgroup by Ellman's reagents as CT₁ = 143.2 μM, CT₂ = 147.4 μM, CT₃ = 151.5 μM, CT₄ = 157.2 μM, CT₅ = 161.8 μM, BT₁ = 168.3 μM, BT₂ = 172.5 μM, BT₃ = 176.7 μM, BT₄ = 196.3 μM, and BT₅ = 205.7 μM. All semen samples were cryopreserved in milk-based extenders by using standard procedures. Post-thaw quality parameters including total and progressive motility, mitochondrial membrane potential, plasma membrane integrity, and acrosome integrity were found to be higher (p < 0.05) in the group (BT₃) containing buffalo milk heated at 110°C, whereas in the same group, lipid peroxidation was found to be lower (p < 0.05) as compared with other treatment groups and control group. In vivo fertility of cryopreserved buffalo sperm was compared among BT₃, CT₁ (conventionally used milk extender), and a Tris egg yolk extender group. The fertility rates [47% (54/114), 30% (33/108), and 36% (37/103)] were higher (p < 0.05) in BT₃ as compared with other groups. This study suggests that buffalo milk heated at 110°C has high antioxidant potential and improves post-thaw quality and in vivo fertility of cryopreserved buffalo bull semen.

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

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

The effect of acrylamide on mitochondrial membrane potential and glutathione extraction in human spermatozoa: A laboratory study

Background

Acrylamide (AA) is a compound used in the industrial production of polyacrylamide. AAs affects by creating oxidative stress. It produces reactive oxygen species and leads to lipid peroxide. Lipid peroxidation in the cell membrane is one of the most important oxidations in the sperm, which can disrupt the fluidity and permeability of cell membranes and damage all cells.

Objective

To investigate the different concentrations of AA on human sperm parameters based on the World Health Organization standard and its impact on mitochondrial membrane potential and sperm glutathione levels.

Materials and Methods

In this laboratory study, we examined the different concentrations of AA on human sperm parameters based on the World Health Organization standard and its impact on mitochondrial membrane potential by flow cytometry and sperm glutathione levels by ELISA assay.

Results

The results were reported as the mean fluorescence intensity of JC and the index was observed to decrease following the effect of AA in mitochondrial membrane potential (Δ Ψm). The results of ELISA test to study the level of intracellular glutathione showed that with the increase in the concentration of AA exposed to sperms, there was a significant reduction in the level of intracellular glutathione.

Conclusion

AA destroys the sperm membrane integrity under apoptotic and oxidative inductions with a negative impact on mitochondrial function and antioxidative enzyme in sperm such as glutathione.

Effect of carboxylated poly l-Lysine as a cryoprotectant on post-thaw quality and in vivo fertility of Nili Ravi buffalo (Bubalus bubalis) bull semen

Buffalo bull sperm are more prone to cryo-injuries. Glycerol being the most common permeable cryoprotectant exerts cytotoxic effects on sperm which cause a reduction in fertility. Thus, the exploration of new cryoprotectant is needed. For this purpose, we investigated the effect of carboxylated poly l-Lysine (CPLL) as cryoprotectant used with different concentrations of glycerol on post-thaw sperm motility, kinematics, plasma membrane integrity, mitochondrial membrane potential (MMP), lipid peroxidation (LPO), catalase concentration and in vivo fertility of Nili Ravi buffalo bull semen. In experiment 1, semen samples (n = 15, bulls = 3) were diluted with Tris-citrate-egg yolk extender containing different concentration of CPLL [0% (C0), 0.25% (C0.25), 0.5% (C0.5), 0.75% (C0.75), 1% (C1)]. Each concentration of CPLL was added in extender containing either 7% (G7) or 5% (G5) glycerol. Diluted semen samples were cooled and cryopreserved using standard procedures. Post-thaw total and progressive motility, plasma membrane integrity, acrosome integrity, and MMP were found higher (P < 0.05) in group (G5C0.75) containing 0.75% CPLL and 5% glycerol as compared to the control group (G7C0) and other groups while LPO was recorded lower (P < 0.05) in the same group (G5C0.75). In experiment 2, in vivo fertility was compared between G5C0.75 (5% Glycerol+ 0.75% CPLL; depicted better post-thaw quality) and control group G7C0. Buffaloes were inseminated after 24 h of onset of estrus. Pregnancy diagnosis was performed per rectum at least 60 days post insemination. The fertility rates [56% (58/102) vs. 36% (37/103)] were higher (P < 0.05) in G5C0.75 as compared to the control group G7C0. Based upon these results, this study concludes that the addition of 0.75% CPLL in combination with 5% glycerol in freezing extender improves the post-thaw structure, function and in vivo fertility of Nili Ravi buffalo bull semen.

Changes in sperm function and structure after freezing in domestic cat spermatozoa

Sperm cryopreservation allows for a long-term storage of genetic. However, changes due to factors as cold shock, osmotic and oxidative stress cause reduction in viability and fertilising ability of frozen/thawed spermatozoa. Therefore, evaluation of cryoinjury of cat spermatozoa is a key factor in achieving better cryopreservation results. This study analysed the changes in structural and functional after freezing in ejaculated domestic cats spermatozoa. Semen samples (n = 60) were analysed before and after freezing, progressive motility was determined with computer-assisted sperm analysis and viability, and acrosome intact spermatozoa, mitochondrial function and superoxide anion ( O 2 - ) were assessed by flow cytometry. The results demonstrated that cryopreservation induced changes in all sperm parameters (p < 0.05). Total sperm motility, viability, acrosome integrity and mitochondrial function of fresh samples were near to 80% and decrease near to 40% in frozen/thawed spermatozoa (p < 0.05); nevertheless, in contrast to all other sperm parameters, the sperm positive with O 2 - increased post/thawing (p < 0.05). In conclusion, changes in frozen/thawed spermatozoa could be related to the effect of oxidative stress due to the increase in the synthesis of O 2 - and a concomitant loss of functional competence. Therefore, the evaluation of these sperm parameters could contribute to complement the analysis of fresh or frozen semen used ART.