The influence of certain aminoacids and vitamins on post-thaw fish sperm motility, viability and DNA fragmentation

Cryopreserved sperm does not affect larval ontogeny and quality in Rhamdia quelen

Fish sperm cryopreservation is an important technique for optimizing juvenile production in aquaculture stations and laboratories and contributing to the conservation of endangered species. Despite its benefits, the cryopreservation process can cause cellular damage, affecting spermatozoa quality and offspring viability. This study aimed to evaluate the larval development of jundiá Rhamdia quelen originating from cryopreserved sperm. Larvae were obtained from artificial reproduction using oocyte samples from four females combined with fresh (Control) or cryopreserved/thawed sperm. The semen was diluted in the cryoprotective solution (1:3 ratio) consisting of skimmed milk powder (5%), methanol (10%), and fructose (5%), and was packaged into 0.25 mL straws. The straws were then stored and cooled in liquid nitrogen vapor for 18 h. The straws were individually warmed in a water bath at 25 °C for 10 s to thaw the samples. The experiments were performed in triplicates. Sperm quality, fertilization, hatching, and larval development were evaluated. After larval hatching, six larval collections were performed (5, 10, 15, 20, and 25 days after hatching), and 15 larvae were sampled per collection per treatment. Cryopreservation reduced sperm motility (70.48 ± 7.70 fresh to 41.36 ± 4.80 cryopreserved semen), progressivity (3874 fresh to 2505 cryopreserved semen), and beat cross frequency (55.83 ± 155 fresh to 50.22 ± 190 cryopreserved semen). Increased the percentage of sperm with abnormal morphology and increased most sperm pathologies. Furthermore, the fertilization rate was lower in the cryopreserved group (63.1 ± 18, and 83.72 ± 7.59 for fresh semen), while hatching was not different between groups (65.3 ± 18.05 fresh, 48.89 ± 21.77 cryopreserved semen) Otherwise, the initial larval development morphology showed no difference in the appearance of structures such as the presence of the vitelline structure, pigmentation pattern, development of the anal pore, embryonic membrane, eye, barbells, notochord flexion, and fin rays, for both treatments. There was no significant difference in the frequency of structures between larvae from fresh and cryopreserved/thawed sperm, revealing a similar developmental pattern in both treatments. In conclusion, the cryopreservation protocol affects sperm quality; however, those sperm able to fertilize the oocytes originate normal larvae with regular larval development of R. quelen up to 25 days old.

Unravelling spermatogenesis in spotted wolffish: Insights from the ultrastructure of juvenile male testes to the cryopreservation of broodstock sperm

The aim of this study was to deepen our understanding of the reproductive biology of male spotted wolffish (Anarhichas minor) using two different experimental approaches involving juvenile and mature broodstock fish. The first approach consisted of a detailed histological examination of the testes to identify the onset of gonadal maturation and characterise the spermatogenic stages in two- and three-year-old juvenile specimens. Light microscopy analysis revealed clear differences between the age groups. Two-year-old fish displayed well-defined interstitial tissue, Sertoli cells and cysts housing spermatogonia stem cells in which meiosis had not yet begun. In contrast, three-year-old fish exhibited cysts containing spermatocytes, spermatids and abundant spermatozoa, indicating the initiation of the spermatogenic cycle, albeit with asynchronous puberty. Histochemical staining revealed a significant presence of smooth myoid cells in the interstitial tissue of sexually mature fish, while electron microscopy further revealed synaptonemal complexes indicating the onset of meiosis and centriolar structures that gave rise to flagella. The second approach focused on optimising semen freezing and cryopreservation procedures in mature broodstock individuals over the age of 10 years. Seven freezing extenders (KT, TS-2, OP, MT, MH, HBSS, or SR), with seawater (SW) as a control, were assessed along with two cryoprotectants dimethylsulfoxide (DMSO) or methanol to evaluate their impact on pre- and post-thaw semen quality. Results showed that the MT and HBSS extenders were superior in total sperm kinetics at 1:3 dilution, and that DMSO showed optimal results in sperm motility and velocity variants. Moreover, the MT and HBSS groups demonstrated consistent sperm viability after cryopreservation, with values similar to fresh samples. Based on the viability results of the SYBR-green-14/PI assay comparing fresh and cryopreserved sperm using MT and HBSS, the MT extender emerged as the most effective freezing medium for cryopreservation of spotted wolffish broodstock sperm. In conclusion, this study provides a comprehensive understanding of the reproductive dynamics of male spotted wolffish, offering valuable insights for both scientific research and aquaculture management.

Energy metabolism and spermatogenesis

Infertility has become a significant health burden around the globe as it is believed that 15 % of married couples struggle with infertility, with half of the problem accrued to the male. The issue of male infertility could be traced to insufficient or absence of spermatozoa. Glucose metabolism is essential for continued spermatogenesis and for the reproductive potential of sperm cells. Appropriate nutrition is critical in maintaining reproductive function as caloric restriction along with weight reduction, excessive food consumption and obesity are harmful to reproductive function. The link between metabolism and reproduction is tied to metabolic hormones like insulin, leptin and thyroid, extracellular environment, mitochondria function, nutrient substrate, availability, and environmental stressors. Although matured spermatozoa utilize glucose directly, it is not the preferred energy substrate for germ cells as they rely on Sertoli cells to supply lactate. The reproductive potential of sperm cells depends on certain modifications like hyperactivated motility, which is mainly dependent on glucose metabolism. Without other energy sources, spermatozoa utilize their internal lipid stores. The uptake and metabolism of glucose by sperm are essential endpoints for determining the potential fertility of male individuals. The biological energy in sperm cells fuels all the physiological processes they engage in, from their deposition in the female reproductive tract to the point where they fertilize an egg. This article thus reviews facts pertinent to the energy metabolism of male germ cells and Sertoli cells.

Exposure to silver and titanium dioxide nanoparticles at supra-environmental concentrations decreased sperm motility and affected spermatozoa subpopulations in gilthead seabream, Sparus aurata

Marine pollution by nanoparticles (NPs) can be reprotoxic for fish and disturb successful reproduction of wild populations. In gilthead seabream (Sparus aurata), a mild effect on sperm motility was observed after exposure to high concentrations of silver NPs. Considering the great heterogeneity traits within a sperm sample, it is possible that NPs affect spermatozoa accordingly, modulating subpopulation profile. Thus, this work aimed to analyse NP effects in sperm motility in general and considering spermatozoa population structure, using a subpopulation approach. Seabream sperm samples from mature males were exposed for 1 h to increasing concentrations of titanium dioxide (1, 10, 100, 1000 and 10,000 μg L-1) and silver (0.25, 25 and 250 μg L-1) NPs, including Ag NP and Ag+, dissolved in a non-activating medium (0.9 % NaCl). Concentrations chosen include realistic (10-100 and 0.25 μg L-1, respectively, for TiO2 and Ag) and supra-environmental values. The mean particle diameter was determined as 19.34 ± 6.72 and 21.50 ± 8.27 nm in the stock suspension, respectively, for titanium dioxide and silver. After the ex vivo exposure, sperm motility parameters were determined using computer-assisted sperm analysis, and sperm subpopulations were later identified using a two-step cluster analysis. Results revealed a significant reduction in total motility after exposure to the 2 highest concentrations of titanium dioxide NPs, while curvilinear and straight-line velocities were not altered. Exposure to silver NPs (Ag NP and Ag+) lowered significantly total and progressive motilities at all concentrations, while curvilinear and straight-line velocities were significantly lower only at the highest concentration. Sperm subpopulations were also affected by the exposure to both titanium dioxide and silver NPs. In both cases, the highest levels of NPs triggered a decrease in the percentage of fast sperm subpopulations (38.2% in TiO2 1000 μg L-1, 34.8.% in Ag NP 250 μg L-1, and 45.0% in Ag+ 250 μg L-1 vs 53.4% in the control), while an increase on slow sperm subpopulations. A reprotoxic effect was proven for both NPs, but only at supra-environmental concentrations.

Addition of Cryoprotectant DMSO Reduces Damage to Spermatozoa of Yellow Catfish (Pelteobagrus fulvidraco) during Cryopreservation: Ultrastructural Damage, Oxidative Damage and DNA Damage

Spermatozoa cryopreservation protocols have been established for yellow catfish (Pelteobagrus fulvidraco), but cryopreservation can still cause cellular damage and affect spermatozoa viability and fertility. Therefore, the aim of this paper was to evaluate the effects of adding or not adding cryoprotectants during low-temperature storage on the ultrastructural damage, oxidative damage, and DNA damage of thawed yellow catfish spermatozoa. The mixed semen of three male yellow catfish was divided into a fresh spermatozoa group, a frozen spermatozoa group (DMSO+) with a cryoprotectant (10% DMSO), and a frozen spermatozoa group without a cryoprotectant (DMSO-). Ultrastructural of the spermatozoa after thawing were observed under an electron microscope and the spermatozoa were assayed for SOD, MDA, and T-AOC enzyme activities, as well as for DNA integrity. In terms of movement parameters, compared with DMSO-, the addition of DMSO has significantly improved sperm motility, curve line velocity (VCL), and straight line velocity (VSL). The ultrastructural results showed that although thawed spermatozoa exhibited increased damage than fresh spermatozoa, 10% DMSO effectively reduced the damage to the plasma membrane, mitochondria, and flagellum of spermatozoa by cryopreservation, and most of the spermatozoa were preserved with intact structure. The results of oxidative damage showed that compared with frozen spermatozoa, 10% DMSO significantly increased the activities of SOD and T-AOC enzymes and clearly reduced the activity of the MDA enzyme. The antioxidant capacity of spermatozoa was improved, lipid peroxidation was reduced, and the oxidative damage caused by cryopreservation was mitigated. The DNA integrity of spermatozoa showed that 10% DMSO clearly reduced the DNA fragmentation rate. In conclusion, 10% DMSO can effectively reduce the ultrastructural damage, oxidative damage, and DNA damage of yellow catfish spermatozoa during cryopreservation; it can also further optimize the cryopreservation protocol for yellow catfish spermatozoa. Meanwhile, it also provides a theoretical basis for the future optimization of the cryopreservation protocols.

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.

Effect of type and concentration of antioxidant on sperm motility, viability, and DNA integrity of climbing perch Anabas testudineus Bloch, 1792 (Pisces: Anabantidae) post-cryopreservation

Sperm quality is preserved through the crucial involvement of antioxidants, which play a vital role in minimizing the occurrence of reactive oxygen species (ROS) during the cryopreservation process. The suitability of the type and concentration of antioxidants are species-dependent, and this study is crucial in order to improve the quality of the climbing perch sperm post-cryopreservation. Therefore, this study aimed to determine the best type and concentration of antioxidants for cryopreservation of climbing perch Anabas testudineus sperm. To achieve this, 6 types of antioxidants, namely, ascorbic acid, beta-carotene, glutathione, butylated hydroxytoluene (BHT), myo-inositol, and alpha-tocopherol, with inclusion of a control were tested in 3 replications at three concentration levels of 0 mg/L (control), 20 mg/L, 40 mg/L, and 60 mg/L. Sperm was diluted in a glucose-base extender at a ratio of 1:60 (sperm: glucose base), then 10 % DMSO and 5 % egg yolk was added before cryopreservation for two weeks. The results showed that the type and concentration of antioxidants had a significant effect on the motility and viability of cryopreserved climbing perch sperm (P < 0.05), where the best results for ascorbic acid, beta-carotene, glutathione, myo-inositol, and alpha-tocopherol were obtained at a concentration of 60 mg/L, while BHT was at a concentration of 20 mg/L. The best results for glutathione, myo-inositol, and alpha-tocopherol were significantly different from other treatments, while the best results for ascorbic acid and beta-carotene (60 mg/L) were not significantly different from the 40 mg/L concentration, while the best results for BHT were not significantly different from the control treatments. Therefore, the best concentration of glutathione, myo-inositol, and alpha-tocopherol was 60 mg/L, while for ascorbic acid and beta-carotene it was 40 mg/L, and BHT was not recommended. DNA integrity analysis indicated the absence of fragmentation in all samples, including fresh, control, and treated sperm. Based on practical and economic considerations, myo-inositol at 60 mg/L was recommended for cryopreservation of climbing perch A. testudineus sperm.

Successful cryopreservation in biodegradable containers of sperm from aquaculture Mediterranean fishes

We aimed to evaluate the efficiency of hard-gelatin and hard-hydroxypropyl methylcellulose (HPMC) capsules as biodegradable alternative containers to plastic straws in European eel (Anguilla anguilla), gilthead seabream (Sparus aurata) and European sea bass (Dicentrarchus labrax) sperm cryopreservation. Sperm samples from each European eel (n = 12) were diluted 1:8:1 (sperm: extender P1+5 % egg yolk: methanol). Gilthead seabream (n = 12) samples were individually diluted in a cryoprotectant solution of 5 % Me2SO + NaCl 1 % plus BSA (10 mg mL-1) at a ratio of 1:6 (sperm: cryoprotectant solution). European sea bass (n = 10) sperm from each male was diluted in non-activating medium (NAM) at a ratio of 1:5.7 (sperm: NAM), and 5 % of Me2SO was added. The diluted European eel and sea bass sperm aliquots (0.5 mL) were individually filled in plastic straws (0.5 mL), hard-gelatin, and HPMC capsules (0.68 mL). Gilthead seabream diluted sperm (0.25 mL) were filled in plastic straws (0.25 mL) and identical capsules described. All samples were frozen in liquid nitrogen vapor and stored in a liquid nitrogen tank. Sperm kinetic parameters were evaluated by CASA-Mot software. Sperm membrane integrity was performed using a Live and Dead KIT and an epifluorescence microscope. To quantify DNA damage, the alkaline comet assay was performed and TailDNA (TD-%) and Olive Tail Moment (OTM) were evaluated by CaspLab software. Sperm cryopreservation of the three Mediterranean species in straws, gelatin, or HPMC capsules reduced the kinetic parameters and cell membrane integrity. Generally, the post-thawing samples cryopreserved in straws and capsules did not differ for the kinetic parameters and cell membrane integrity, except for European sea bass sperm, where the samples stored in gelatin capsules showed higher velocities (VCL - 100; VSL - 76; VAP - 90 μm s-1) than the sperm stored in HPMC capsules (VCL - 87; VSL - 59; VAP - 73 μm s-1). The cryopreservation process did not damage the sperm DNA of European eel and European sea bass, regardless of the containers used. On the other hand, gilthead seabream sperm cryopreserved in gelatin (TD - 9.8 %; OTM - 9.7) and HPMC (TD - 11.1 %; OTM - 11.2) capsules showed higher DNA damage than fresh samples (TD - 3.6 %; OTM - 2.7) and the sperm stored in straws (TD - 4.4 %; OTM - 5.2). The hard-gelatin and HPMC biodegradable capsules can be used as an alternative to straws for European eel, gilthead seabream, and European sea bass sperm cryopreservation.

Oxidative stress and cryoresistance of sturgeon sperm: A review

Currently, the majority of sturgeons are relict fishes of high economic value yet endangered with extinction. Cryopreservation of sperm has great potential in fish farming and conservation, but the problem of low cryoresistance of sturgeon sperm has not yet been solved. The goal of this work was to review current literature data on the causes of low tolerance of sturgeon sperm to cryodamage. The influence of cryopreservation on the parameters of physiology and metabolism of sturgeon sperm (morphology and fine ultrastructure, mobility and fertilization ability, integrity of the plasma membrane, protein, lipid and metabolite profiles, antioxidant status, DNA damage), as well as on biomarkers of oxidative stress (lipids peroxidation levels and carbonyl derivatives of proteins) is discussed. Since the development of oxidative stress is an important mechanism of sperm cryodamage induction, the review presents the literature on the role of oxygen-derived species in damage of sturgeon reproductive cells caused by cryopreservation. Particular attention is paid to the system of antioxidant protection of sturgeon seminal plasma and spermatozoa, represented by antioxidant enzymes and low molecular weight antioxidants capable of utilizing various reactive forms of oxygen and nitrogen. The review discusses the results of lipidomic and proteomic studies of sturgeon sperm, which made it possible to obtain new data on the lipid composition of cell membranes, to detect proteins involved in the protection of sturgeon spermatozoa from oxidative damage during cryopreservation. This review presents the use of «omics» technology to elucidate the mechanism of cryodamage in sturgeon sperm. Additionally, the review summarizes information on the unique anatomical, morphological, biochemical, and physiological features of sturgeon sperm, which may be associated with low cryoresistance of sturgeon, in order to establish prospects for further research on improving the methods of the conservation of sperm of these threatened species.

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.

L-carnitine solution used on Rhamdia quelen thawed sperm activation boosts sperm movement, maintains larval quality, and permits to optimize the sperm use

The activation of cryopreserved sperm with solutions containing L-carnitine can improve sperm quality after thawing, owing to its involvement in several metabolic pathways. Sperm movement and viability for fertilization, hatching, and larval normality were assessed in Rhamdia quelen thawed sperm activated with L-carnitine solutions. Sperm from 24 males were cryopreserved in 0.25 mL straws. After thawing, the sperm movement was assessed by CASA (Computer-Assisted Sperm Analysis) in samples activated with distilled water containing 0.0 (control), 47.8, 96.2, 144.5, 192.3, and 240.7 mM L-carnitine, and another one with 79.9 mM D-fructose (control). Sperms from another 24 males were cryopreserved in an identical manner and used in the fertilization assays. Considering the sperm movement, fertilization assays were carried out using 0.0, 96.2, and 144.5 mM L-carnitine, and 79.9 mM D-fructose solutions. Greater motility and velocity were achieved with 144.5 mM L-carnitine at 28 and 18 s after activation, respectively. Linearity was not affected by time. The greater mean motility was provided by 144.5 mM as well as the greater mean velocity and linearity by 192.3 mM L-carnitine. Fertilization and hatching were not influenced; however, 144.5 mM L-carnitine and 79.9 mM D-fructose solutions produced more normal larvae. In summary, the L-carnitine solution increased sperm movement and maintained larval quality and production, similar to a conventional fructose activation solution.

Effectiveness of Clinical-Grade Chondroitin Sulfate and Ascorbic Acid in Mitigating Cryoprotectant Toxicity in Porcine Articular Cartilage

High concentrations of cryoprotective agents (CPAs) are required to achieve successful vitrification of articular cartilage; however, CPA cytotoxicity causes chondrocyte death. To reduce CPA toxicity, supplementation with research-grade additives, in particular chondroitin sulfate (CS) and ascorbic acid (AA), have previously been shown to improve chondrocyte recovery and metabolic function after exposure to CPAs at hypothermic conditions. However, it is necessary to evaluate the pharmaceutical equivalent clinical grade of these additives to facilitate the supplementation of additives into future vitrification protocols, which will be designed for vitrifying human articular cartilage in tissue banks. We sought to investigate the effectiveness of clinical-grade CS, AA, and N-acetylcysteine (NAC) in mitigating toxicity to chondrocytes during CPA exposure and removal, and determine whether a combination of two additives would further improve chondrocyte viability. We hypothesized that clinical-grade additives would exert chondroprotective effects comparable to those of research-grade additives, and that this protective effect would be enhanced if two additives were combined when compared with a single additive. The results indicated that both clinical-grade and research-grade additives significantly improved cell viability (p < 0.10) compared with the negative control (CPA with no additives). CS, AA, and NAC+AA increased cell viability significantly (p < 0.10) compared with the negative control. However, NAC, NAC+CS, and CS+AA did not improve cell viability when compared with the negative control (p > 0.10). We demonstrated that supplementation with clinical-grade CS or AA significantly improved chondrocyte viability in porcine cartilage subjected to high CPA concentrations, whereas supplementation with clinical-grade NAC did not benefit chondrocyte viability. Supplementation with clinical-grade additives in CPA solutions can mitigate CPA toxicity, which will be important in translating previously developed effective protocols for the vitrification of articular cartilage to human tissue banks.

Saccharides Influence Sperm Quality and Expressions of Motility and Fertilization-Associated Genes in Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

Pacific abalone, Haliotis discus hannai, is a highly commercial seafood in Southeast Asia. The present study aimed to determine the influence of saccharides and vitamins on post-thaw sperm quality, ATP content, fertilization capacity, hatching capacity, and mRNA content of motility and fertilization-associated genes of Pacific abalone. Sperm cryopreserved using saccharides improved the post-thaw sperm quality including motility, acrosome integrity (AI), plasma membrane integrity (PMI), and mitochondrial membrane potential (MMP). However, vitamins (l-ascorbic acid) did not result in any significant improvement in sperm quality. Sperm cryopreserved using saccharides also improved ATP content, DNA integrity, and mRNA content of motility and fertilization-associated genes of post-thaw sperm than sperm cryopreserved without saccharides. Among sperm cryopreserved using different saccharides, post-thaw sperm quality indicators (except PMI) and mRNA content of motility and fertilization-associated genes did not show significant differences between sperm cryopreserved using 3% sucrose (S) combined with 8% dimethyl sulfoxide (DMSO) and sperm cryopreserved using 1% glucose (G) combined with 8% ethylene glycol (EG). However, sperm cryopreserved using 3% S + 8% DMSO showed higher post-thaw sperm quality (motility: 58.4 ± 2.9%, AI: 57.1 ± 3.2%, PMI: 65.3 ± 3.3%, and MMP: 59.1 ± 3.2%), ATP content (48.4 ± 1.8 nmol/ml), and % DNA in tail (2.09 ± 0.20%) than sperm cryopreserved using other saccharides. When sperms were cryopreserved using 3% S + 8% DMSO, the mRNA content of motility (heat shock protein 70, HSP70; heat shock protein 90, HSP90; protein kinase A, PKA-C; axonemal protein 66.0, Axpp66.0; and tektin-4) and fertilization-associated (sperm protein 18 kDa, SP18 kDa) genes were higher than in sperm cryopreserved using other saccharides. However, changes in the mRNA contents of these genes were insignificant between sperm cryopreserved using 3% S + 8% DMSO and 1% G + 8% EG. Taken together, these results indicate that cryopreservation using 3% S + 8% DMSO can improve post-thaw sperm quality and mRNA contents better than other examined cryoprotectants. The present study suggests that 3% S + 8% DMSO is a suitable cryoprotectant for sperm cryopreservation and molecular conservation of this valuable species.

Antioxidant Activity and Oxidative Stress-Oriented Apoptosis Pathway in Saccharides Supplemented Cryopreserved Sperm of Pacific Abalone, Haliotis discus hannai

The Pacific abalone Haliotis discus hannai is a highly commercialized seafood in Southeast Asia. The aim of the present study was to determine the antioxidant activity and oxidative stress-oriented apoptosis pathway in saccharides supplemented cryopreserved sperm of Pacific abalone. Cryopreserved sperm showed impaired antioxidant defenses due to the reduced mRNA abundance of antioxidant genes (CAT, Cu/Zn-SOD, Mn-SOD, GPx, GR, and BCL-2), apoptosis inhibitor (HSP70, and HSP90) gene, and enzymatic antioxidant activity compared to fresh sperm. Such impaired antioxidant defenses caused an increase in the mRNA expression of apoptosis genes (Bax, and Caspase-3), finally leading to apoptosis. The impaired antioxidant defense also increased O₂^•− production and lipid peroxidation (MDA) levels, which further accelerated apoptosis. Considering all the experimental findings, an apoptosis pathway of cryopreserved sperm has been adopted for the first time. Specifically, sperm cryopreserved using 3% sucrose combined with 8% dimethyl sulfoxide (DMSO) showed improved mRNA stability, enzymatic activity, and DNA integrity with reduced O₂^•− production and MDA levels compared to sperm cryopreserved with the other types of examined cryoprotectants (8% ethylene glycol + 1% glucose, 6% propylene glycol + 2% glucose, 2% glycerol + 3% glucose, and 2% methanol + 4% trehalose). The present study suggests that 3% sucrose combined with 8% DMSO is suitable to cryopreserve the sperm of this valuable species for molecular conservation.

Diet and human reproductive system: Insight of omics approaches

Nutrition and lifestyle have a great impact on reproduction and infertility in humans, as they are essential for certain processes such as implantation, placental growth, angiogenesis, and the transfer of nutrients from the mother to the fetus. The aim of this review is to provide the interconnection between nutrition and reproductive health through the insight of omics approaches (including metabolomics and nutrigenomics). The effect of various macronutrients, micronutrients, and some food‐associated components on male and female reproduction was discussed. Recent research work was collected through database search from 2010 to 2020 to identify eligible studies. Alterations of metabolic pathways in pregnant women were deliberated with an emphasis on different strategies of lifestyle and dietary interventions. Several nutritional methods, which are important for embryonic and child neurological development, nutritional supplements to lactation, and improved gestational length along with birth weight have been emphasized. Considerable advances in omics strategies show potential technological development for improving human reproductive health.

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.

Effects of melatonin supplementation on the quality of cryopreserved sperm in the neotropical fish Prochilodus lineatus

The cryopreservation process causes damage to sperm structures and supplementation of the cryoprotective medium is an alternative to reduce these damages. The aim of this study was to determine the effect of melatonin supplementation on post-thaw sperm quality in Prochilodus lineatus. The cryoprotective medium was supplemented with 2.00, 2.75, 3.50, and 4.25 mM melatonin, and the control group (without melatonin). Sperm motility parameters, membrane integrity, sperm morphology, oxidative stress (lipid peroxidation and enzymatic activity), and fertilization capacity were analyzed in the post-thaw sperm. Samples cryopreserved with 2.00 mM melatonin yielded higher sperm motility rate than other treatments with the addition of melatonin. Sperm curvilinear velocity (VCL) and average path velocity (VAP) were higher in samples containing 2.00 mM melatonin than in other treatments. Samples from control and with 2.00 mM melatonin presented higher membrane integrity and morphological normality than samples containing 4.25 and 2.75 mM melatonin, respectively. Regarding oxidative stress, lower lipid peroxidation (LPO) occurred in 2.75 and 3.50 mM melatonin, compared to control. While higher enzyme activity of catalase (CAT) occurred in the control than in other treatments, no differences were observed in the activity of superoxide dismutase (SOD). Higher fertilization and hatching rates occurred at 2.75 mM melatonin compared to 4.25 mM. Although no significant differences were observed in LPO between the control and samples supplemented with 2 mM melatonin, it was observed that this dosage of melatonin allowed higher VCL and VSL and reduced values of CAT. However, as there are no differences in motility and fertilization rates between the control and the 2 mM concentration, it is suggested that further studies be carried out with lower concentrations of melatonin in order to determine its effectiveness as an antioxidant in the sperm of this species.

Combination of trehalose and low boron in presence of decreased glycerol improves post-thawed ram sperm parameters: A model study in boron research

BACKGROUND

Sperm cryopreservation has been widely used in the field of reproductive biotechnology. It applies to certain males of economic and scientific values, including livestock breeds or endangered animal species. The development of a semen extender with a low cryoprotectant concentration and an appropriate amount of trehalose and boron can prevent the deterioration of sperm parameters.

OBJECTIVE

The main goal of this study is to establish a suitable ram extender model, by examining different combinations of high (5%) and low (3%) glycerol concentrations (to reduce its toxic effects on sperm freezing), a fixed amount of trehalose and an increased dose of boron to prevent the deterioration of sperm parameters, and investigate the levels of gene expressions.

MATERIALS AND METHODS

The Merino ram ejaculates were collected. The collected ejaculates providing the defined criteria were pooled. The pooled ejaculates were divided into eight aliquots and diluted with the Tris extender including different combinations of glycerol (5% and 3%) and boron (0.25, 0.5, and 1 mm) concentrations and a fixed amount of trehalose, then frozen. After freeze-thawing process, sperm motility, mitochondrial membrane activity, plasma membrane integrity, acrosomal membrane integrity, DNA damage (single cell gel electrophoresis (COMET) and TUNEL assays) as well as NAD(P)H quinone oxyreductase (NQO1), glutamate-cycteine ligase (GCLC), and glutathione S-transferase (GSTP1) for molecular mechanisms of sperm cell response to oxidative stress were assessed for different extender groups following freeze-thawing process: 5% glycerol + 0 mm boron (G5B0.00), 5% glycerol + 0.25 mm boron (G5B0.25), 5% glycerol + 0.5 mm boron (G5B0.50), 5% glycerol + 1 mm boron (G5B1.00), 3% glycerol + 0 mm boron (G3B.00), 3% glycerol + 0.25 mm boron (G3B0.25), 3% glycerol + 0.5 mm boron (G3B0.50), and 3% glycerol + 1 mm boron (G3B1.00).

RESULTS

G3B0.25 presented higher percentages of subjective motility, mitochondrial activity, and viability of spermatozoa comparing with G5B0.00 and groups with boron. Supplementation of 0.25 mm boron with and without trehalose (G3B0.25 and G5B0.25) showed higher acrosome integrity, compared with G5B0.00, G5B1.00, G3B0.50, and G3B1.00. For TUNEL analysis, G3B1.00 showed the highest DNA integrity among the experimental groups which was statistically significant only with G5B0.50 (p < 0.05). The mRNA levels of NQO1 were significantly decreased in G5B1.00, G3B0.50, and G3B1.00, when compared to G5B0.00. In comparison with G5B0.00, supplementation of 1 mm boron with and without trehalose had significantly lower expression of GCLC. The level of GSTP1 gene was significantly lower (approximately threefold) in G3B1.00, compared to G5B0.00 (p < 0.05).

DISCUSSION AND CONCLUSION

It can be assumed that the increase of the boron concentration in the extender may have important adverse effects on sperm parameters and antioxidant gene expression after thawing. The results obtained from this study will help to understand the toxicity limits of boron and eliminate the toxicity of glycerol in studies of gametes and tissue freezing. Therefore, it can be concluded that the use of sufficient boron can decrease cryodamages of cryopreservation of mammalian spermatozoa as well tissue engineering.

Melatonin and canthaxanthin enhances sperm viability and protect ram spermatozoa from oxidative stress during liquid storage at 4°C

Antioxidants are used to minimize oxidative stress during liquid semen storage. The main aim of current study was to elucidate effect of supplementing melatonin and canthaxanthin in Tris-based extender could enhance seminal quality of ram at 4°C up to 72 h. A total of 48 ejaculates were collected from breeding Magra rams (n = 8) and were preliminarily subjected for various macroscopic and microscopic semen evaluation tests. These ejaculates were pooled and divided into three equal aliquots. Two aliquots were diluted (1:10) using extender encompassing final concentration of 1mM melatonin and 25 µM canthaxanthin and stored at 4°C. Third aliquot with extender only was kept as control. Structural and functional seminal changes were observed at different time points of preservation. Results revealed that mean values for progressive sperm motility, viability and total antioxidant capacity were significantly higher (p < 0.05) in melatonin group while hypo-osmotic swelling test was significantly (p < 0.05) higher in canthaxanthin group. Total sperm abnormalities and malondialdehyde levels were significantly (p < 0.05) lower in both treatment groups indicating their antioxidant efficacy in protection of spermatozoa from oxidative stress. Results of study indicated that supplementation of these antioxidants to ram semen could be used to enhance storage life of liquid semen at 4°C up to 72 h.

L-proline as a novel additive to cryopreservation media improved post-thaw quality of human spermatozoon via reducing oxidative stress

Sperm cryopreservation as a routine technique in assisted reproductive technique (ART) laboratories has detrimental effects on spermatozoa. Various methods have been introduced to improve it. The aim of this research was to evaluate the effects of L-proline supplementation in cryopreservation medium on normozoospermic semen samples. A total of 30 semen samples were collected from normozoospermic men. Cryopreservation media were supplemented with different concentrations of L-proline (0, 1, 2 and 4 mmol/L). The semen samples were cryopreserved. After thawing, sperm parameters and chromatin integrity (aniline blue (AB), toluidine blue (TB), sperm chromatin dispersion test (SCD) and chromomycin A3 (CMA3)), reactive oxygen species (ROS), and total antioxidant capacity (TAC) and malondialdehyde (MDA) levels were evaluated. A total of 4 mmol/L L-proline significantly improved progressive motility and viability (p < 0.05). MDA and ROS levels significantly diminished in samples were cryopreserved by 4 mmol/L L-proline supplemented cryopreservation media (p < 0.001). Also, it significantly increased TAC level. Also, chromatin damages (AB, TB and CMA3) significantly improved in samples were cryopreserved by 4 mmol/L L-proline supplemented cryopreservation media (p < 0.05). The results support that the usage of L-proline supplemented cryopreservation media to improve sperm quality after cryopreservation.

Supplementation of the freezing medium with Coenzyme Q10 attenuates oxidative stress and improves function of frozen-thawed giant grouper (Epinephelus lanceolatus) spermatozoa

Incorporation of Coenzyme Q10 (CoQ10) to the freezing medium provides advantageous effect for sperm cryopreservation in a variety of animal species, yet which has not been tested in giant grouper (Epinephelus lanceolatus). This research was designed to elucidate if CoQ10 could be used as a potential additive to improve giant grouper sperm quality after cryopreservation. After the process of freezing and thawing, various sperm quality parameters including motility, viability, apoptosis, mitochondrial membrane potential (MMP), intracellular reactive oxygen species (ROS) generation, DNA fragmentation as well as fertilization rate were evaluated with CoQ10 added at concentrations of 0, 25, 50 and 100 μM. Compared to the control group (0 μm), addition of CoQ10 in the medium yielded significantly higher total motility and curvilinear velocity, whereas the progressive motility, straight-line velocity and average path velocity were not differ from each other. An obvious improvement in viability was observed in spermatozoa cryopreserved with 25 and 50 μM CoQ10, while the apoptosis rate in CoQ10 treated groups (25, 50 and 100 μM) exhibited significantly lower values than that of the control. Besides, the production of ROS was significantly decreased with CoQ10 addition groups when compared with the control. In consistent with the improvement in antioxidant defense, CoQ10 supplementation in the medium also enhanced mitochondrial activity and reduced DNA fragmentation. In addition, freezing medium supplemented with CoQ10 also improved the fertilization success, a significantly higher fertilization rate was recorded at the concentration of 50 μM, but this value was not differ from that of 25 μM. Overall, the antioxidant CoQ10 provided an obvious beneficial effect on post-thaw quality of giant grouper spermatozoa. It was concluded that the optimal concentration of CoQ10 is 50 μM in the freezing medium.

Oxidative Stress and DNA Damage of Zebrafish Sperm at Different Stages of the Cryopreservation Process

Although gamete cryopreservation has facilitated advancement of reproduction research by allowing the storage of cells over prolonged periods of time, during freezing-thawing cycles, cells inevitably suffer from cryoinjuries. Here, we evaluate oxidative stress and DNA damage of zebrafish sperm at different stages of the cryopreservation process. It was generally observed that the freezing and thawing of the samples led to an increase in the generation of reactive oxygen species and the activity of the catalase enzyme and a reduction in the generation of sulfhydryl groups and superoxide dismutase activity. The alkaline comet assay demonstrated that DNA damage increased after equilibration time, with an even greater increase after freezing and thawing. The comet assay modified with the enzyme formamidopyrimidine glycosylase, and Endonuclease III demonstrated greater DNA damage than the standard comet assay, demonstrating a high degree of oxidation of purines and pyrimidines at all stages of cryopreservation. Our results show that the freeze and thaw processes cause greater oxidative stress and DNA damage than cryoprotectant toxicity during exposure at the equilibrium stage.

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.

Metabolomic differences of seminal plasma between boars with high and low average conception rates after artificial insemination

Seminal plasma is a complex biological fluid containing many metabolites including amino acids, fructose, carbohydrates and lipids Metabolites play important roles in multiple biological processes, but details and significance of the seminal plasma metabolome related to boar fertility are unknown. The aim of the present study was to compare the comprehensive metabolome of seminal plasma from boars with different conception rate after artificial insemination and to identify the potential biomarkers. Semen samples were collected from boars which divided into two groups according to the conception rates in the offspring. Seminal plasma metabolites were isolated, purified, and then subjected to Ultra-high Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-qTOF-MS) procession. A total of 576 (Positive ion mode) and 377 (Negative ion mode) metabolites were identified in seminal plasma. Metabolites were identified and categorized according to their major chemical classes, including carboxylic acids and derivatives, organooxygen compounds, amino acids, peptides, and alogues, fatty amides, fatty acyls, benzene and substituted derivatives, purine nucleotides, pyrimidine nucleotides, glycosyl compounds, fatty acids and conjugates. The results showed that 4-Aminobenzoate, Pro-Asn, Ile-Tyr, Homoveratric acid and D-Biotin were higher in semen of boar with higher conception rate (HG) versus lower conception rate (LG) (p < .05), whereas L-Serine, Butoxyacetic acid, S-Methyl-5'-thioadenosine, Capsaicin and 1-O-(cis-9-Octadecenyl)-2-O-acetyl-sn-glycero-3-phosphocholine (PAF) were lower in HG than in LG (p < .05). These metabolites may be considered as candidate biomarkers for different fertility in boars.

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.

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.

Short-term storage sperm of coho salmon (Oncorhynchus kisutch) at 4 °C: Effect of sperm: Extender dilution ratios and antioxidant butyl-hydroxytoluene (BHT) on sperm function

Short-term storage of semen is a necessary key procedure in fish; it allows maximizing the use of gametes. Nevertheless, sperm quality decreases during storage has been associated with oxidative stress damage due to an increase in reactive oxygen species (ROS) during storage. This study was designed to optimize a short-term storage protocol for Coho salmon (Oncorhynchus kisutch) spermatozoa, evaluating the effect of extender dilution and the addition of butyl-hydroxytoluene (BHT) antioxidant on sperm function parameters. In the first experiment, fresh semen was diluted in Storfish®: extender dilution (1:2 and 1:3) and a control sample undiluted and stored at 4 °C for 7-days. In both experiments motility (MO), viability and integrity of plasma membrane, mitochondrial membrane potential (MMP) and superoxide anion level (O₂^-) were evaluated at 0, 3 and 7 days. Result shows that, 1:3 dilution maintained a higher sperm function for a longer period time. In the second experiment, spermatozoa were suspended in Storfish® (1:3) supplemented with two different concentrations of BHT (1.0 mM and 2.0 mM) and a control sample without antioxidant and stored at 4 °C for 7 days. The results demonstrated that, antioxidant-supplemented samples greater MO than control samples (P < 0.05). The viability remained >75% during storage in all groups. MMP was higher in 2.0 mM BHT compared to 1.0 mM and control (P < 0.05), in addition, this concentration reduced O₂^- level (P < 0.05). In conclusion, sperm: extender dilution 1:3 and adding of 2.0 mM BHT in sperm storage extender may enhance protection sperm function in Oncorhynchus kisutch against effects harmful of the oxidative stress during the in vitro storage.

Effect of different concentrations of resveratrol on the quality and in vitro fertilizing ability of ram semen stored at 5 °C for up to 168 h

The aim of the study was to investigate the effects of different concentrations of resveratrol on head morphology, motility characteristics, oxidative state and in vitro fertility of cooled ram spermatozoa. Pooled semen from three Najdi rams was diluted with Triladyl® having different concentrations of resveratrol, zero (control), 200 μM (45.65 μg/mL) and 400 μM (91.30 μg/mL) resveratrol, then stored at 5 °C for 168 h. The head morphometric, sperm kinematic parameters, Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and in vitro fertilizing capability of ram spermatozoa were evaluated after 24, 72, 120 and 168 h of cooling storage. The total motility (TM) of the sperm with resveratrol at 200 μM and 400 μM was significantly (p ≤ 0.05) higher than that in the control group at 72 and 120 h of cooling storage. On the other hand, the progressive motility (PM) of the sperm with resveratrol at 200 μM and 400 μM was significantly (p ≤ 0.05) higher than that in the control group at 168 h of cooling storage period. After 168 h of cooling storage, significantly higher straightness (STR) was observed in 400 μM group than two other groups and in 200 μM group than the control group. Both resveratrol groups had higher linearity (LIN) than control one at 120 and 168 h of cooling storage. The length, width and area of sperm head were lower (P ≤ 0.05) in the control compared to the other treatment groups after 120 and 168 h of storage. There was a significant increase in superoxide dismutase (SOD) concentration in the two resveratrol groups compared with the control one over the seven days of cooling storage and the same result was found in the reduced glutathione (GSH) concentration at 24, 72, and 168 h of storage. There was a significant (p ≤ 0.05) decrease in malondialdehyde (MDA) concentration in the 400 μM resveratrol group than that in two other groups over the seven days of storage period. Cleavage and blastocyst rates following in vitro fertilization were significantly higher (p ≤ 0.05) in 400 μM resveratrol than other groups at 72 h for cooling storage period. In conclusion, addition of resveratrol in the extender can protect sperm head morphology, improve kinematic parameters and in vitro fertility, and reduce oxidative stress of ram spermatozoa during liquid storage at 5 °C.

Cryoprotectants synergy improve zebrafish sperm cryopreservation and offspring skeletogenesis

The synergy obtained by the combination of cryoprotectants is a successful strategy that can be beneficial on the optimization of zebrafish sperm cryopreservation. Recently, a protocol was established for this species using an electric ultrafreezer (-150 °C) performing cooling rate (-66 °C/min) and storage within one step. The ultimate objective of sperm cryopreservation is to generate healthy offspring. Therefore, the objective of this study was to select the most adequate cryoprotectant combination, for the previously established protocol, that generate high quality offspring with normal skeletogenesis. Among the permeating cryoprotectant concentrations studied 12.5% and 15% of N,N-dimethylformamide (DMF) yielded high post-thaw sperm quality and hatching rates. For these two concentrations, the presence of bovine serum albumin (10 mg/mL), egg yolk (10%), glycine (30 mM) and bicine (50 mM) was evaluated for post-thaw sperm motility, viability, in vitro fertilization success and offspring skeletal development (30 days post fertilization). Higher concentration of permeating cryoprotectant (15%) decreased the incidence of deformed arches and severe skeletal malformations, which suggests higher capacity to protect the cell against cold stress and DNA damage. Extender containing 15% DMF with Ctrl, Bicine and egg yolk were the non-permeating cryoprotectants with higher post-thaw quality. The use of these compounds results in a reduction in vertebral fusions, compressions and severity of skeletal malformations in the offspring. Therefore, these extender compositions are beneficial for the quality of zebrafish offspring sired by cryopreserved sperm with -66 °C/min freezing rate. To the best of our knowledge, this is the first report on skeletal development of the offspring sired by cryopreserved sperm performed with different freezing media compositions in zebrafish.

Sperm motility in fish: technical applications and perspectives through CASA-Mot systems

Although a relatively high number of sperm quality biomarkers have been reported over the years in several fish species, sperm motility is nowadays considered the best biomarker for fish spermatozoa. The first scientific reports focusing on fish sperm motility date from a century ago, but the objective assessment allowed by computer-aided sperm analysis (CASA-Mot) systems was not applied to fish species until the mid-1980s. Since then, a high number of sperm kinetic parameters from more than 170 fish species have been reported in more than 700 scientific articles, covering a wide range of topics, such as sperm physiology, sperm storage, broodstock management, the phenomenon of sperm competition, ecotoxicology and understanding the life cycle of the species. The sperm kinetic parameters provided by CASA-Mot systems can serve as powerful and useful tools for aquaculture and ecological purposes, and this review provides an overview of the major research areas in which fish sperm motility assessment by a CASA-Mot system has been used successfully.

The roles of reactive oxygen species and antioxidants in cryopreservation

Cryopreservation has facilitated advancement of biological research by allowing the storage of cells over prolonged periods of time. While cryopreservation at extremely low temperatures would render cells metabolically inactive, cells suffer insults during the freezing and thawing process. Among such insults, the generation of supra-physiological levels of reactive oxygen species (ROS) could impair cellular functions and survival. Antioxidants are potential additives that were reported to partially or completely reverse freeze-thaw stress-associated impairments. This review aims to discuss the potential sources of cryopreservation-induced ROS and the effectiveness of antioxidant administration when used individually or in combination.

Canthaxanthin protects human sperm parameters during cryopreservation

Different antioxidants have been introduced to reduce oxidative stress during the cryopreservation. The main goal of this study was to evaluate the effects of canthaxanthin on human sperm parameters during the freeze-thaw process. This study was performed on 25 normozoospermic semen samples dividing into five groups including 0, 0.1, 1, 10, and 25 µM of canthaxanthin. The prepared spermatozoa were cryopreserved by rapid freezing technique. Sperm motility, viability (eosin-nigrosin), morphology (Papanicolaou), acrosome reaction (double staining), DNA denaturation (acridine orange), chromatin packaging (aniline blue and toluidine blue), and DNA fragmentation (sperm chromatin dispersion test) were evaluated before freezing and after thawing. All sperm parameters after thawing significantly were decreased compared to before freezing. Twenty-five micromolar canthaxanthin could significantly improve the progressive and total motility, viability, normal morphology, chromatin packaging, acrosome integrity and DNA denaturation and fragmentation. Ten micromolar canthaxanthin significantly improved total motility, viability, normal morphology, chromatin packaging, acrosome integrity and DNA denaturation and fragmentation. Whereas, in 1 µM group, there were significant differences only in improvement of acrosome integrity, chromatin packaging (toluidine blue) and DNA denaturation and fragmentation. But, in 0.1 µM group, there were no significant differences in any of measured parameters. It seems that canthaxanthin ameliorates detrimental effects of cryopreservation on human sperm parameters.

Effects of cooling rates on the quality of Prochilodus lineatus (Valenciennes, 1836) sperm

This study aims to investigate the effect of different cooling rates on the semen cryopreservation of curimba (Prochilodus lineatus). Nineteen ejaculates were obtained from adults males and cryopreserved at 15°C/min (CR15), 30°C/min (CR30) (controlled temperature inside and outside straw, speed was stable during freezing) and direct freezing in liquid nitrogen vapour (~35.6°C/min) (CRNV). The straws were thawed and seminal parameters evaluated. DNA fragmentation through the comet assay was assessed. A fresh sperm sample was not frozen and used for analyses. Data were submitted to an analysis of variance (ANOVA), and means were compared by Scott-Knott test (p < 0.05) using the R Software. Mean motility percentage was 100%, and motility duration was 39.5 ± 5.7 s for the fresh sperm (subjective analysis); 58.9 ± 8.0% and 24.5 ± 5.7 s for CR15; 64.8 ± 4.8% and 26.5 ± 7.1 s for CR30; and 50.1 ± 16% and 25.7 ± 4.7 s for CRNV, respectively. Motility percentages were higher and equal between CR15 and CR30 compared to CRNV (p < 0.05). Some sperm motion kinetics, namely average path velocity (VAP) and straight line velocity (VAS), were higher for CR30 (p < 0.05), while curvilinear velocity (VCL) and velocity progression (PRO) were lower for CRNV (p < 0.05). Straightness (STR) and wobble (WOB) were the same among treatments (p > 0.05). Sperm morphology results indicated higher means for total morphological sperm alterations in CRNV. All cooling rates caused sperm DNA fragmentation, although CR30 provided a less harmful effect. This is the first report for cryopreserved P. lineatus sperm preserved under different controlled cooling rates. The cooling rate of 30°C/min is indicated for the cryopreservation of this fish sperm as it led to the lowest detrimental spermatozoa effects.

Use of trehalose in the semen cryopreservation of Amazonian catfish Leiarius marmoratus

The current study assessed a semen cryopreservation protocol in the Amazonian catfish Leiarius marmoratus, a freshwater fish, of rheophilic behavior, and of great importance for Brazilian fish farming. Eight males (n = 8) were stripped and the semen was cryopreserved if total motility in fresh semen was higher than 80%. The external cryoprotectant Trehalose was then diluted in Beltsvile Thawing Solution (BTS) extender in the following concentrations: 50, 100, 150, and 200 mM. Semen samples were diluted in the media (1:9 v/v) being tested, then frozen in a container with nitrogen vapor (dryshipper), and stored in liquid nitrogen at -196 °C. Motility parameters assessed post-thawing were performed by CASA-system and sperm cell integrity analyses (membrane integrity, DNA integrity, and mitochondrial function) were performed through fluorescence microscopy. As a result, no significant statistical difference was observed between treatments, independently of Trehalose concentrations tested in the following post-thawing analysis: membrane integrity, DNA integrity, mitochondrial functionality, and sperm motility duration. As of total and progressive motilities, the treatment containing 50 mM trehalose (15.6 and 9.5%, respectively), exhibited inferior results when compared to treatments with 150 mM (22.9 and 17.7%, respectively) and 200 mM (31.4 and 26.3%, respectively) trehalose concentrations (P < 0.05); however, it did not differ from the treatment with 100 mM trehalose (18.6 and 15.3%, respectively). Therefore, treatments with trehalose at higher concentrations exhibited superior results when compared to other treatments in in vitro motility parameters for L. marmoratus.

Hypotaurine Is a Substrate of GABA Transporter Family Members GAT2/Slc6a13 and TAUT/Slc6a6

Hypotaurine is a precursor of taurine and a physiological antioxidant that circulates in adult and fetal plasma. The purpose of the present study was to clarify whether hypotaurine is a substrate of Slc6a/gamma-aminobutyric acid (GABA) transporter family members. Radiolabeled hypotaurine was synthesized from radiolabeled cysteamine and 2-aminoethanethiol dioxygenase. The uptakes of [³H]GABA, [³H]taurine, and [¹⁴C]hypotaurine by HEK293 cells expressing mouse GAT1/Slc6a1, TAUT/Slc6a6, GAT3/Slc6a11, BGT1/Slc6a12, and GAT2/Slc6a13 were measured. TAUT and GAT2 showed strong [¹⁴C]hypotaurine uptake activity, while BGT1 showed moderate activity, and GAT1 and GAT3 showed slight but significant activity. Mouse TAUT and GAT2 both showed Michaelis constants of 11 µM for hypotaurine uptake. GAT2-expressing cells pretreated with hypotaurine showed resistance to H₂O₂-induced oxidative stress. These results suggest that under physiological conditions, TAUT and GAT2 would be major contributors to hypotaurine transfer across the plasma membrane, and that uptake of hypotaurine via GAT2 contributes to the cellular resistance to oxidative stress.

Seminal plasma amino acid profile in different breeds of chicken: Role of seminal plasma on sperm cryoresistance

Seminal plasma is a key biological fluid that modulates sperm function in the reproduction process. However, its role in sperm biotechnologies is scarce in poultry. The aims of the present study were to study the amino acids profile and total proteins of seminal plasma in 12 Spanish chicken breeds and to investigate the role of seminal plasma on cryoresistance of rooster sperm. To investigate the role of seminal plasma on cryoresistance, diluted pooled semen samples were cryopreserved in the presence and absence of seminal plasma. Glutamic acid was the most abundant free amino acid in seminal plasma, followed by alanine, serine, valine, and glycine. There was an influence of breed (P<0.05) on the percentage of viable sperm after freezing-thawing of samples with seminal plasma. Cluster analysis revealed that White Prat, Black Castellana, Blue Andaluza, Quail Castellana, and Red-Barred Vasca returned the best freezing-thawing response (good freezers). There was a positive correlation between seminal plasma concentrations of valine, isoleucine lysine, leucine and post thaw viability. The evaluation of fertilization capacity of frozen-thawed semen from the breeds White Prat ('good freezer') and Black-Red Andaluza ('bad freezer') showed that good freezer had higher fertility (20/68, 29.4%) compared to bad freezer breed (14/76, 18.4%), even if the difference was not significant (P = 0.08). The TUNEL assay revealed that freezing/thawing procedures in presence of seminal plasma provoked higher DNA fragmentation in most of the breeds, with a positive correlation between seminal alanine, valine, isoleucine, methionine, leucine, tyrosine, phenylalanine concentrations and DNA integrity. DNA fragmentation was lower in absence of seminal plasma and the breed effect on sperm viability was highly reduced. It is concluded that specific seminal plasma amino acids were associated with post-thaw percentage of viable sperm and DNA integrity. The removal of seminal plasma decreases the variability of the results and DNA fragmentation damages.

Cryoprotective effect of glutamine, taurine, and proline on post-thaw semen quality and DNA integrity of donkey spermatozoa

This study was conducted to evaluate the effect of amino acid addition to semen on post-thaw quality of donkey spermatozoa. Eighteen ejaculates were pooled and divided into aliquots which were cryopreserved in Gent A^® containing 1% ethylene glycol (Gent-EG) and supplemented with 0 (as control), 20, 40, or 60 mM of glutamine, proline, or taurine. The greatest concentration (60 mM) of glutamine and taurine resulted in greater (P < 0.001) post-thaw sperm motility. Amino acid supplementation did not improve (P > 0.05) sperm morphology and membrane plasma integrity compared with the control samples. Whereas, improvement (P < 0.05) of acrosome integrity was observed with use of 60 mM glutamine. After thawing, there were no differences (P > 0.05) in the sperm DNA fragmentation index (sDFI) among treatments. The 60 mM glutamine and 40 mM taurine treatments, however, resulted in a reduction (P < 0.05) in sDFI values in the first 6 h of semen incubation, compared with the control samples. At 24 h, the sDFI values were less (P < 0.05) in all supplemented as compared with control samples, except for the 20 mM proline treatment group. In conclusion, supplementation of the Gent-EG extender with glutamine or taurine at 60 mM improved post-thaw donkey sperm quality. The addition of proline to the freezing extender, however, did not provide any significant enhancement in sperm quality, compared with the control group.

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

High levels of reactive oxygen species (ROS), which may be associated with reduced sperm quality, can be detected during cryopreservation of sperm of some species. Our objective was to investigate whether the addition of antioxidants to cryopreservation extenders influenced post-thaw sperm characteristics and fertility in Acipenser dabryanus, Acipenser sinensis and Acipenser baerii. Prior to freezing, sperm samples were diluted with a base extender as control or in extender supplemented with catalase (CAT), glutathione (GSH), cysteine (NAC), ascorbic acid (VC) or their paired combinations. Protective concentrations of CAT, GSH and VC in the three species were 25 U/ml, 0.25-0.5 mg/ml and 0.5 mg/ml, respectively. Cysteine showed no protective effect against ROS. The addition of CAT, GSH and VC positively affected either acrosome or membrane integrity of post-thawed sperm in the three species, as well as spermatozoan motility in A. sinensis. The combination of antioxidants did not show a positive synergistic effect. This study suggested that the use of antioxidants in the cryopreservation of sturgeon sperm has potential to decrease intracellular ROS, and consequently preserve acrosome and membrane integrity, as well as spermatozoan motility.

Storage and transportation of Prochilodus lineatus (Characiformes) sperm prior to cryopreservation

In this study we compared post-thaw quality of P. lineatus sperm frozen shortly after collection, with sperm frozen after dilution and transportation, and up to 6h from collection. From each sperm sample (n=10 males) five aliquots were taken. One aliquot was diluted in the freezing medium (1 sperm:8 glucose:1 methyl glycol) and frozen ∼20min after collection in the field (control), while the other four aliquots were transported to the laboratory where freezing took place 3 or 6h after collection. From the transported aliquots, two were diluted 1:4 in glucose solution before transportation (diluted samples), while the other two were kept undiluted until freezing (undiluted samples). Thus the five treatments were: control, undiluted-3h, diluted-3h, undiluted-6h and diluted-6h. Post-thaw sperm was evaluated for membrane integrity, motility rate and velocities (curvilinear=VCL; average path=VAP; straight line=VSL). Post-thaw membrane integrity did not differ among the five treatments (48-60% intact sperm). Sperm motility rate was similar (P>0.05) between control (64%) and undiluted samples (60-62%) and higher (P<0.05) than that in diluted samples (35-45%), regardless the time after collection when freezing took place. Velocities were higher in control and in undiluted-3h samples (VCL of 254-265μm/s, VAP of 219-244μm/s and VSL of 134-147μm/s) than in diluted samples or samples frozen 6h after collection. P. lineatus sperm can be transported/shipped to the laboratory without decreasing its suitability for cryopreservation. Sperm should be kept undiluted during storage and be frozen within 3h.

Progress, challenges and perspectives on fish gamete cryopreservation: A mini-review

Protocols for the cryopreservation of fish gametes have been developed for many different fish species, in special, freshwater salmonids and cyprinids. Methods for sperm freezing have progressed during the last decades due to the increasing number of potential applications: aquaculture (genetic improvement programs, broodstock management, helping with species having reproductive problems), biotechnology studies using model fish species (preservation of transgenic or mutant lines), cryobanking of genetic resources from endangered species, etc. This mini-review tries to give an overview of the present situation of this area of research, identifying the main challenges and perspectives, redirecting the reader to more in-depth reviews and papers.

Morphometric comparison by the ISAS® CASA-DNAf system of two techniques for the evaluation of DNA fragmentation in human spermatozoa

DNA fragmentation has been shown to be one of the causes of male infertility, particularly related to repeated abortions, and different methods have been developed to analyze it. In the present study, two commercial kits based on the SCD technique (Halosperm ® and SDFA) were evaluated by the use of the DNA fragmentation module of the ISAS ® v1 CASA system. Seven semen samples from volunteers were analyzed. To compare the results between techniques, the Kruskal-Wallis test was used. Data were used for calculation of Principal Components (two PCs were obtained), and subsequent subpopulations were identified using the Halo, Halo/Core Ratio, and PC data. Results from both kits were significantly different (P < 0.001). In each case, four subpopulations were obtained, independently of the classification method used. The distribution of subpopulations differed depending on the kit used. From the PC data, a discriminant analysis matrix was obtained and a good a posteriori classification was obtained (97.1% for Halosperm and 96.6% for SDFA). The present results are the first approach on morphometric evaluation of DNA fragmentation from the SCD technique. This approach could be used for the future definition of a classification matrix surpassing the current subjective evaluation of this important sperm factor.

Cryopreservation of Atlantic salmon Salmo salar sperm: effects on sperm physiology

The objective of this study was to determine the effect of freezing on the function in Atlantic salmon Salmo salar spermatozoa. The semen was frozen in Cortland's medium + 1.3M dimethyl sulphoxide + 0.3M glucose + 2% bovine serum albumin (final concentration) in a ratio of 1:3 (semen:cryoprotectant) as the treatment (T) and fresh semen as the control (F). Straws of 0·5 ml of sperm suspension were frozen in 4 cm of N2 L. They were thawed in a thermoregulated bath (40° C). After thawing, the percentage of spermatozoa with fragmented DNA [transferase dUTP (deoxyuridine triphosphate) nick-end labelling (TUNEL)], plasma membrane integrity (SYBR-14/PI) and mitochondrial membrane potential (ΔΨMMit, JC-1) were evaluated by flow cytometry and motility was evaluated by optical microscope under stroboscopic light. The fertilization rates of the control and treatment semen were tested at a sperm density of 1·5 × 10(7) spermatozoa oocyte(-1) , by observation of the first cleavages after 16 h incubation at 10° C. In the cryopreserved semen (T), the mean ± s.d. DNA fragmentation was 4·8 ± 2·5%; plasma membrane integrity 75·2 ± 6·3%; mitochondrial membrane potential 51·7 ± 3·6%; motility 58·5 ± 5·3%; curved line velocity (VCL ) 61·2 ± 17·4 µm s(-1) ; average-path velocity (VAP ) 50·1 ± 17·3 µm s(-1) ; straight-line velocity (VSL ) 59·1 ± 18·4 µm s(-1) ; fertilization rate 81·6 ± 1·9%. There were significant differences in the plasma membrane integrity, mitochondrial membrane potential, motility, fertilization rate, VCL , VAP and VSL compared with the controls (P < 0·05). Also the mitochondrial membrane potential correlated with motility, fertilization rate, VCL and VSL (r = 0·75; r = 0·59; r = 0·77 and r = 0·79, respectively; P < 0·05); and the fertilization rate correlated with VCL and VSL (r = 0·59 and r = 0·55, respectively).

Influence of Glutamine Supplementation on Motility and Fertilization Success of Frozen-Thawed Persian Sturgeon (Acipenser persicus) Sperm

Amino acids have an important biological role for the prevention of cell damage during cryopreservation. The aim of this study was to investigate the effects of glutamine on post-thaw sperm motility and fertilization success in the Persian sturgeon (Acipenser persicus). Sperm collected from six fish was cryopreserved in extenders containing different glutamine concentrations (2.5, 5 and 10 mm). Sperm samples diluted at the ratio of 1 : 1 using the extenders were subjected to cryopreservation. After dilution, the sperm suspensions were sucked into 250-μl straws; the straws were placed on the tray, frozen in nitrogen vapour and plunged into liquid nitrogen. Then, sperm were thawed in a water bath at 40°C for 5 s and used for analysis. Our results revealed that an increase in the concentration of glutamine caused a significant increase in the motility percentage, curvilinear velocity (VCL) and also fertilization success in the Persian sturgeon (p < 0.05). Comparing all concentrations of glutamine, the best concentration for sperm motility and fertilization rate was 10 mm. In addition, higher post-thaw motility percentage, VCL, and fertilization and hatching rates were obtained with the extender at the concentration of 10 mm (p < 0.05). The findings of this study showed that glutamine was of greater benefit to Persian sturgeon sperm motility during frozen-thawed process.

Sperm dilution ratio affects post-thaw motility rate and velocity of Prochilodus lineatus (Characiformes) sperm

There is a lack of standardization in sperm cryopreservation of aquatic organisms and, thus, a necessity of more accurate investigations in all steps of this process. In this study, the effects of sperm dilution ratio on post-thaw sperm quality of Prochilodus lineatus were evaluated. Sperm was diluted in a standard freezing medium (glucose and methyl glycol) at four different ratios (sperm to final volume = 1:5, 1:10, 1:50 or 1:100), frozen in a nitrogen vapour vessel at -170°C and then stored in liquid nitrogen vessel at -196°C. Post-thaw motility rate and velocities (curvilinear = VCL; average path = VAP; straight line = VSL) were determined using a Computer-Assisted Sperm Analyzer (CASA) at 10 and 40 s post-activation. The highest motility rates were observed when sperm was frozen at a ratio of 1:5 (76%) and 1:10 (75%). The highest VCL (225 μm/s) and VAP (203 μm/s) were observed at a ratio of 1:10, while VSL was similar among samples frozen at 1:5, 1:10 and 1:50 (97-124 μm/s). When those parameters were evaluated again 30 s later, motility decreased significantly in samples frozen at a ratio of 1:5 (57%) and 1:10 (61%), while velocities decreased significantly in all samples regardless of dilution ratio (75-85 μm/s of VCL, 38-53 μm/s of VAP and 25-39 μm/s of VSL). P. lineatus sperm should be frozen at a ratio of 1:10, where both the number of loaded sperm per straw and the post-thaw quality are maximized.