Antioxidant supplementation, effect on post-thaw spermatozoan function in three sturgeon species

Quercetin in semen extender curtails reactive oxygen and nitrogen species and improves functional attributes of cryopreserved buck semen

Cryopreservation of goat spermatozoa is challenging due to several factors, including one of the most essential, i.e., oxidative stress. It is particularly essential in goat semen due to its scanty ejaculate volume and high sperm concentration. This leaves a narrow sperm-to-seminal plasma ratio owing to marginal antioxidant support; moreover, semen extension further dilutes the antioxidant level, leading to an imbalance of oxidant-antioxidant equilibrium. The present study aimed to evaluate the effect of quercetin on curtailing oxidative stress and its reflection on the post-thaw survivability and membrane integrity of goat spermatozoa. For this study, six bucks were selected. Six ejaculates from each buck totaling 36 ejaculates were collected, which were then split into five parts; furthermore, each part was added with a semen extender having a particular concentration of additive. Group C without quercetin and T1 containing Vitamin E at 3 mmol/mL were considered the control and positive control respectively, whereas T2, T3, and T4 contain 10, 20, and 30 μmol/mL of Quercetin respectively. The final sperm concentration of each group was kept at 200 × 106 spermatozoa/mL. All groups were subjected to equilibration at 4 °C for 4 h, then filled in French mini (0.25 mL) straws, followed by sealing and cryopreservation. Samples after 72 h of cryopreservation were subjected to evaluation of plasma membrane integrity and viability through staining, acrosomal integrity, and mitochondrial membrane activity through flow cytometry. Evaluation of sperm kinematics as well as the oxidant-antioxidant status of sperm (ROS and nitric oxide) and seminal plasma (SOD, CAT, GPx, FRAP, and lipid peroxidation through MDA estimation) were also carried out. Quercetin, when supplemented at 20 μmol/mL in buck semen extender, significantly (p < 0.01) improved cryopreserved sperm functions in terms of plasma membrane integrity, viability, acrosomal integrity, mitochondrial membrane activity, and sperm kinematics of buck semen. Similarly, Quercetin supplementation at 20 μmol/mL significantly reduced reactive oxygen and nitrogen species (RONS) in sperm and improved the antioxidant status of seminal plasma, which was indicated by reduced oxidative damage and improved the antioxidant status of buck semen. In conclusion, Quercetin at 20 μmol/mL reduced oxidative stress, improved semen antioxidant status, and improved sperm membranes integrity and kinematics.

Supplementation of Extender with Melatonin Improves the Motility, Mitochondrial Membrane Potential, and Fertilization Ability of Cryopreserved Brown-Marbled Grouper Sperm

Sperm cryopreservation is a valuable tool for breeding, conservation, and genetic improvement in aquatic resources, while oxidative damage will cause a decline in sperm quality during this progress. Melatonin (MT), a natural antioxidant hormone, is used as an additive in sperm cryopreservation to reduce cellular damage from oxidative stress. Here, we aimed to investigate the effect of adding MT to the freezing medium in sperm cryopreservation of brown-marbled grouper (Epinephelus fuscoguttatus). Different concentrations of MT (0, 0.1, 0.25, and 0.5 mg/mL) were tested. We evaluated sperm motility, viability, apoptosis, mitochondrial membrane potential (MMP), and fertilization ability to assess the effects of MT supplementation. Our results demonstrated that the addition of MT to the extender improved the post-thaw motility, MMP, and fertilization ability of brown-marbled grouper sperm. The total motility, curvilinear velocity, straight linear velocity, and average path velocity in MT-treated groups (0.1 and 0.25 mg/mL) exhibited significantly higher values than that of the control group. A higher MMP (p < 0.05) was observed in the group treated with 0.25 mg/mL MT, suggesting that supplementation of MT in the extender might be able to protect mitochondrial membrane integrity effectively. Regarding fertilizing ability, 0.25 mg/mL MT yielded a significantly higher hatching rate than the control. An adverse effect was found with the concentration of MT up to 0.5 mg/mL, suggesting the possible toxicity of a high-dose addition. In this study, we optimized the sperm cryopreservation protocol of brown-marbled grouper, which might be valuable for sperm cryopreservation and sample commercialization of groupers and other fish.

Effects of taurine, cysteine and melatonin as antioxidant supplements to the freezing medium of Prochilodus brevis sperm

Cryopreservation consist of a set of methods to preserve cells and tissues by drastically reducing the temperature. Among some undesired effects, cryopreservation might generate reactive oxygen species that lead to an increase of oxidative stress, causing damage to cells. This study aimed to test taurine, cysteine, and melatonin on the freezing of Prochilodus brevis sperm and assess its effects on post-thawed sperm quality. Sperm was collected and seven pools were formed (n = 7). They were diluted (1:9) in standard medium (5% glucose, 10% dimethyl sulfoxide and 5% egg yolk) supplemented or not (control) with taurine (0.3, 1.0, 3.16 or 10.0 mM), cysteine (0.3, 1.0, 3.16 or 10.0 mM) or melatonin (0.6, 1.12, 2.0 or 3.56 mM). Post-thawed sperm was evaluated for kinetic (total motility, velocities, and percentage of rapid cells), morphology and membrane and DNA integrity. Differences were found when melatonin was used as an antioxidant. For the variables rapid sperm and sperm velocities, 3.56 mM melatonin presented higher results than the control (melatonin 0 mM). Melatonin 2 mM was similar to 3.56 mM on rapid sperm, average path velocity (VAP) and curvilinear velocity (VCL). No difference was found between concentration 0 mM (control) and taurine treatments. As for cysteine, 0.3 mM presented the best results for rapid sperm than 10 mM, and higher VCL and VAP than 1 mM. Melatonin 3.56 mM presented higher results on kinetic parameters (rapid motility, VCL, VSL and VAP) than other tested antioxidants. Therefore, melatonin 3.56 mM is recommended to be added to the sperm freezing medium of P. brevis.

Effects of supplementation of cryopreservation media with cysteine on the post-thaw quality and fertility of brown-marbled grouper (Epinephelus fuscoguttatus) spermatozoa

The cryopreservation process is associated with the generation of excessive reactive oxygen species, which causes a series of cellular damage to spermatozoa. The objective of the current study was to investigate the effect of different concentrations of cysteine on post-thaw sperm quality of brown-marbled grouper sperm. Semen samples were frozen with cysteine supplemented at 0.5, 1, 2, 5, 10 mM and the control group (no additive). After thawing, sperm quality parameters were analyzed. In comparison to the control, cysteine treatment groups yielded relatively higher sperm total motility, progressive motility, and curvilinear velocity. Different concentrations of cysteine had no effect on average path velocity, straight linear velocity and viability (P > 0.05), while an increase in the concentration of cysteine resulted in a significant improvement in the mitochondrial membrane potential, SOD activity, and ATP content (P < 0.05). As for lipid peroxidation, the extent of which in cysteine treated spermatozoa was less than the control, although the differences were not statistically significant (P > 0.05). In terms of fertilizing capacity, a greater hatching rate (91.7 ± 1.2%) was obtained in thawed sperm treated with 2 mM cysteine, compared to the control (84.3 ± 4.2%; P < 0.05). Overall, it is concluded that the addition of cysteine is helpful in maintaining the function of frozen-thawed brown-marbled grouper sperm, which can be recommended as an effective antioxidant to improve the semen cryopreservation efficiency.

Use of cryoprotectors and antioxidants in sturgeon semen cryopreservation

In recent years, the possibility of increasing the low cryoresistance of sturgeon sperm by using antioxidants in basic cryoprotective media has been studied. The goal of this work was to review the current literature on impact of the cryoprotectors, well-known antioxidants and new multifunctional compounds on the activity indicators and fertilizing capability of sperm, as well as on biomarkers of cryostress. A special attention is given to the radical scavenging activity of studied compounds in relation to the highly reactive oxygen species, to prevent and negate oxidative stress damage of sturgeon sperm. Also, new trends for future research through the application of novel polyfunctional antioxidants to sturgeon sperm cryopreservation were indicated.

The Protective Role of Melatonin in Sperm Cryopreservation of Farm Animals and Human: Lessons for Male Fish Cryopreservation

Simple Summary

In recent years, cryopreservation of fish sperm has been a rapidly evolving technique that contributes both to the improvement of genetic reproduction programs and the proper management of broodstock as well as to ensuring the viability of endangered species. However, this technique can cause significant damage to sperm, making the use of cryoprotectants and antioxidants in cryopreservation solutions imperative. The hormone melatonin has demonstrated positive effects on the cryopreservation of sperm in both farm animals and humans. Therefore, the plethora of research that has been conducted on animals and humans could be expanded to fish cryopreservation, making melatonin potentially a very promising alternative cryoprotectant.

Abstract

Cryopreservation is a technique that offers various advantages, especially in fish, among others, that makes the reproduction of species easier through a constant supply of sperm, synchronization of the gamete availability of both sexes, storage of semen for genetic improvement programs, reduction in the cost by eliminating the need to maintain male broodstock, and conserving the gametes of endangered species. However, freezing and warming procedures for cryopreservation lead to a reduction in the quality and viability of cryopreserved sperm because of oxidative stress. For this reason, the enrichment of extender media with antioxidants is a common method of cryopreservation of the semen of several fish species. Recently, many studies have been published for the protective role of antioxidants and especially of melatonin on male fertility preservation both in farm animals and humans, demonstrating the beneficial effects of melatonin as a sperm cryoprotectant. On the other hand, very few studies were conducted using melatonin as an antioxidant in different male fish species for semen cryopreservation. We conclude that the use of moderate concentrations of melatonin are beneficial to semen preservation, and the mechanisms through which melatonin acts positively on spermatozoa need to be further investigated to establish improvement protocols for cryopreservation in fish species.

Is catalase an effective additive to alleviate oxidative stress during cryopreservation of zebrafish sperm at the repository level?

The goal of this study was to investigate whether supplementation of cryoprotective medium with catalase (CAT), an antioxidation enzyme, is efficient for zebrafish sperm cryopreservation from the viewpoint of high-throughput genetic repository operations. Three cryoprotectants (10%, v/v), dimethylacetamide (DMA), dimethylformamide (DMF), and methanol were used. The objectives were to evaluate the effects of CAT on sperm motility, plasma membrane integrity, and concentration for: 1) fresh sperm at equilibration up to 60 min; 2) post-thaw sperm after cooling at 10, 20, and 40 °C/min), and 3) post-thaw fertilization and embryo survival rates. Catalase addition did not improve sperm motility, regardless of the cryoprotectants added. After 10-min exposure to DMA or methanol, membrane integrity was significantly decreased (70-75%) compared to controls. With catalase, sperm cells maintained membrane integrity and after 50 min equilibration, cell concentrations were maintained with CAT compared to cryoprotectant-only test groups. However, after cryopreservation and thawing, CAT did not affect the outcome of motility, membrane integrity, cell concentration, fertilization, or embryo survival assays. Analysis of cooling rates also indicated that CAT did not affect 3-hpf fertilization or 24-hpf survival rates. Overall, addition of CAT could provide some protection of sperm from oxidative stress before freezing, but not after thawing. We propose that decisions concerning routine use of CAT for repositories, especially those handling tens of thousands of frozen samples per year, would depend on whether efficient high-throughput operation, or specific research questions are programmatic goals.

The interference of ozone gas in kinects and mitochondrial potential of equine sperm submitted on cryopreservation

The objective of this study was to evaluate the effects of the addition of different concentrations of ozone to quarter horse semen submitted to cryopreservation. Six ejaculates from four stallions were collected and were divided in four experimental groups: a control group (BotuCRIO® extender) and three other groups with BotuCRIO® ozonized at concentrations of 6, 8 and 12 μg of O₃/mL. The semen samples were diluted (200 x 10⁶ spermatozoa/mL), filled in straws and frozen. After thawing (37 ºC, 30s), the samples were evaluated at 0, 30 and 60 minutes of incubation regarding sperm kinetics by a computer-assisted sperm analysis (CASA), and plasma membrane integrity (PMI), acrosome integrity (ACi) and mitochondrial membrane potential (MMP) by fluorescent probes. There was a reduction in the kinetic parameters total motility (TM), progressive motility (PM), curvilinear velocity (VCL), straight line velocity (VSL) and average path velocity (VAP) in all groups during the thermoresistance test (TT), a pattern also found in PMI and MMP analyses (p<0.05). There was no difference (p>0.05) between the control and treatment (6, 8, and 12 μg of O₃/mL) groups, in any of the evaluated times for the kinetic parameters TM, linearity (LIN), straightness (STR), wobble index (WOB), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF). Regarding the VCL, VSL and VAP parameters, the group treated with 6 μg did not differ from the control or from 8 μg, but was higher than 12 μg at 30 and 60 minutes. ACi and PMI did not differ between groups (p>0.05), but PMI was lower in groups 8 μg and 12 μg compared to the control and 6 μg (p<0.05). It was concluded that the addition of ozone does not present beneficial effects for cryopreservation of equine semen at the concentrations used and decreases important parameters of fertility.

Antioxidants in Fish Sperm and the Potential Role of Melatonin

In recent years, the effects of novel antioxidants have played an important role in the research focusing on fish cell protection. As food demand grows, aquaculture production becomes more intensive, and fish are more exposed to oxidative stress conditions, like high densities, temperature shifting, frequent fish handling and samplings, and prophylactic or disease treatments, which expose fish to a different environment. Particularly in reproduction, germ cells lose antioxidant capacity with spermatogenesis, as spermatozoa are more prone to oxidative stress. Antioxidants have been used in a variety of fish physiological problems including in reproduction and in the establishment of cryopreservation protocols. From the most used antioxidants to natural plant food and herbs, and endogenously produced antioxidants, like melatonin, a review of the literature available in terms of their effects on the protection of fish spermatozoa is presented here in a classified structure. Several direct and indirect approaches to improve gamete quality using antioxidants administration are mentioned (through feed supplementation or by adding in cryopreservation media), as well as factors affecting the efficiency of these molecules and their mechanisms of action. Special attention is given to the unclear melatonin pathway and its potential scavenger activity to prevent and counteract oxidative stress damage on fish spermatozoa.

GFc7 as a Smart Growth Nanofactor for ex vivo Expansion and Cryoprotection of Humans' Hematopoietic Stem Cells

Background

Nowadays, smart synthesized nanostructures have attracted wide attention in the field of stem cell nanotechnology due to their effect on different properties of stem cells.

Methods

GFc7 growth nanofactor was synthesized based on nanochelating technology as an iron-containing copper chelator nanocomplex. The effect of this nanocomplex on the expansion and differentiation of hematopoietic stem cells (HSCs) as well as its performance as a cryoprotectant was evaluated in the present study.

Results

The results showed that the absolute count of CD34⁺ and CD34⁺CD38^- cells on days 4, 7, 10 and 13; the percentage of lactate dehydrogenase enzyme on the same days and CD34⁺CXCR4 population on day 10 were significantly increased when they were treated with GFc7 growth nanofactor in a fetal bovine serum (FBS)-free medium. This medium also led to delayed differentiation in HSCs. One noticeable result was that CD34⁺CD38^- cells cultured in an FBS medium were immediately differentiated into CD34⁺CD38⁺ cells, while CD34⁺CD38^- cells treated with GFc7 growth nanofactor in FBS medium did not show such an immediate significant differentiation. De-freezing GFc7-treated CD34⁺ cells, which were already frozen according to cord blood bank protocols, showed a higher percentage of cell viability and a larger number of colonies according to colony-forming cell assay as compared to control.

Conclusion

It can be claimed that treating HSCs with GFc7 growth nanofactor leads to quality and quantity improvement of HSCs, both in terms of expansion in vitro and freezing and de-freezing processes.

Cryoprotective activity of phosphorus-containing phenol

The antioxidant and cryoprotective efficiencies of a 3,5-di-tert-butyl-4-hydroxyphenyl)methylenediphosphonic acid (MDPA) differ significantly for sperm cells of various species of sturgeon fish (Russian sturgeon, beluga and Stellate sturgeon). The ability of phosphorus-containing phenol MDPA to decrease the level of lipid peroxidation of sperm, beneficial effect on the activity indicators of the sperm of native sturgeon and of the defrosted one after deep freezing as well as on the fertility of sperm cells was shown.

Effect of alpha-lipoic acid on oxidative stress, viability and motility in the common carp (Cyprinus carpio) spermatozoa after short-term storage and cryopreservation

As known for different metabolic functions, α-lipoic acid (ALA) has been tested for spermatozoa preservation of animals as well as of human, but not for fish spermatozoa. The present study determined the effects of ALA on short and long-term (cryopreservation) preservation of common carp (Cyprinus carpio) spermatozoa, for the first time. For that, spermatozoa were diluted in extenders containing 0 (control), 0.025, 0.05, 0.1, 0.5, 1, 2, 5, and 10 mM of ALA concentrations in both short-term preservation and cryopreservation. Spermatozoa motility parameters by computer-assisted semen analysis, viability, lipid peroxidation and catalase activity in spermatozoa were conducted in both 2nd and 120th hours of short-term storage and post-thaw samples. Higher percentages of total spermatozoa motility (80 ± 3) and viability (87 ± 3) were observed in 0.5 mM ALA group after 120 h of incubation. In post-thaw samples, higher percentages of these parameters were in 1 mM ALA group (74 ± 3 and 83 ± 2, respectively). Moreover, the results have shown that the addition of ALA until concentrations of 2 mM improved especially spermatozoa curvilinear velocity, maintained viability, and suppressed excessive lipid peroxidation during the preservations. In conclusion, the additions of 0.5 mM ALA for short-term preservation and 1 mM ALA for cryopreservation were the optimal concentrations, and shown the protective effects on common carp spermatozoa, when considering all measured parameters together.

Catechol thioethers with physiologically active fragments: Electrochemistry, antioxidant and cryoprotective activities

A number of asymmetrical thioethers based on 3,5-di-tert-butylcatechol containing sulfur atom bonding with physiologically active groups in the sixth position of aromatic ring have been synthesized and the electrochemical properties, antioxidant, cryoprotective activities of new thioethers have been evaluated. Cyclic voltammetry was used to estimate the oxidation potentials of thioethers in acetonitrile. The electrooxidation of compounds at the first stage leads to the formation of o-benzoquinones. The antioxidant activities of the compounds were determined using 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) assay, experiments on the oxidative damage of the DNA, the reaction of 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro, and iron(II) chelation test. Compounds 1-9 have greater antioxidant effectiveness than 3,5-di-tert-butylcatechol (CatH₂) in all assays. The variation of physiologically active groups at sulfur atom allows to regulate lipophilic properties and antioxidant activity of compounds. Thioethers 3, 4 and 7 demonstrate the combination of radical scavenging, antioxidant activity and iron(II) binding properties. The researched compounds 1-9 were studied as possible cryoprotectants of the media for cryopreservation of the Russian sturgeon sperm. Novel cryoprotective additives in cryomedium reduce significantly the content of membrane-permeating agent (DMSO). A cryoprotective effect of an addition of the catechol thioethers depends on the structure of groups at sulfur atom. The cryoprotective properties of compounds 3, 4 and 7 are caused by combination of catechol fragment, bonded by a thioether linker with a long hydrocarbon chain and a terminal ionizable group or with a biologically relevant acetylcysteine residue.