Enhancing Cryopreserved Sperm Quality in Chinese Rare Minnow Gobiocypris rarus: The Impact of Antifreeze Proteins

The Chinese rare minnow (Gobiocypris rarus), an important model fish in China, faces endangerment in the wild. Sperm cryopreservation facilitates the development of new strains and germplasm conservation, but the quality of its cryopreserved sperm remains low. This study evaluates the protective effects of different concentrations of antifreeze proteins (AFP I and AFP III) on the cryopreservation of Chinese rare minnow sperm. Cryopreserved sperm showed significant declines in progressive motility, curvilinear velocity (VCL), average path velocity (VAP), and lifespan compared to fresh sperm, except for straight-line velocity (VSL). The cryomedium containing 10 μg/mL AFP I improved these parameters to their highest levels. However, no significant difference was found in progressive motility and kinetic parameters between cryopreserved sperm with and without AFPs. Cryopreserved sperm with 10 μg/mL AFP I showed the highest plasma membrane integrity, mitochondrial activity, and DNA integrity, significantly better than without AFPs; importantly, the fertilization rate of cryopreserved sperm with 10 μg/mL AFP I was not significantly different from that of fresh sperm. These results indicate that the addition of 10 μg/mL AFP I to the cryomedium for Chinese rare minnow sperm does not improve kinetic parameters but significantly enhances sperm quality, aiding in its new strain development and germplasm conservation.

Regulation of winter wheat-originated antifreeze glycoprotein on rooster spermatozoa freezability

The freezability of chicken spermatozoa is low, therefore, effective cryoprotectants is desiderated. Antifreeze proteins (AFPs) are widely found in cold-tolerant species and help them to survive in freezing environments. This study was the first to evaluate the effects of different concentrations of plant-originated antifreeze glycoprotein (AFGP) (0, 0.1, 1, and 5 μg/mL) on post-thawed sperm motion characteristics, morphology, mitochondrial function, antioxidant activity, and fertilizing potential in chickens. Results showed that the total motility of 0.1 to 1 μg/mL AFGP groups were significantly higher than those of the 5 μg/mL AFGP group (P < 0.05). The post-thawed sperm viability of 0.1 μg/mL AFGP group was significantly higher than any of test groups (P < 0.05). Higher abnormal morphology rate of post-thawed sperm was observed in the control group (0 μg/mL AFGP) than in the 0.1, 1, and 5 μg/mL AFGP groups (P < 0.05). The concentrations of malondialdehyde (MDA) decreased gradually with the increase of AFGP concentration. ATP was significantly higher in the 0.1 and 1 μg/mL AFGP groups than those of control and any of test groups (P < 0.05). The 0.1 to 1 μg/mL AFGP groups had increased mitochondrial membrane potential (MMP) level (P > 0.05). The 0.1 μg/mL AFGP group had the highest average fertility (61.36%) compared with control group (57.02%) and any of test groups of chickens at 31 wk of age, and the 1 μg/mL AFGP group had the highest average fertility (37.72%) compared with control group (21.73%) and any of test groups of chickens at 65 wk of age. In conclusion, the results from this study suggest lower concentration of AFGP (0.1-1 μg/mL) showed positive effect for sperm function. This study inspires the continuous evaluation and seeking right way of adopting different kinds of AFPs in rooster semen cryopreservation.

A brief review of the methodology and cryoprotectants in selected fish and mammalian species

Cryopreservation is a valuable technique used to assist in the genetic improvement of cultured stocks and provide a continuous supply of good-quality semen for artificial insemination. Conserving semen by cryopreservation serves several purposes (e.g. artificial reproductive technologies and species conservation) and is also used in the clinical treatment of human infertility. However, the lifespan of cryopreserved semen is influenced by a range of factors, including storage temperature, cooling rate, chemical composition of the extender, the concentration of cryoprotectant, reactive oxygen species, seminal plasma composition and hygienic control. The choice of cryoprotectant is a vital factor underlying the success of animal semen cryopreservation. In this regard, extensive research has been carried out on various cryoprotectants, such as egg yolk, dimethyl sulfoxide, methanol, ethylene glycol and dimethylacetamide. Recent studies have also described the use of a range of new cryoprotectants for cryopreservation, including compounds of plant origin (soy), amino acids, antifreeze proteins, carbohydrates and cyclodextrins. Moreover, semen cryopreservation and storage require the use of liquid nitrogen or ultralow refrigeration methods for both long- and short-term storage. This review summarizes the general methods used for freezing semen and discusses the use of traditional and newly emerging cryoprotectants (permeable and non-permeable) for the cryopreservation of semen in selected fish and mammalian species.

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.

Novel Apoplastic Antifreeze Proteins of Deschampsia antarctica as Enhancer of Common Cell Freezing Media for Cryobanking of Genetic Resources, a Preliminary Study

Antifreeze proteins (AFPs) are natural biomolecules found in cold-adapted organisms that lower the freezing point of water, allowing survival in icy conditions. These proteins have the potential to improve cryopreservation techniques by enhancing the quality of genetic material postthaw. Deschampsia antarctica, a freezing-tolerant plant, possesses AFPs and is a promising candidate for cryopreservation applications. In this study, we investigated the cryoprotective properties of AFPs from D. antarctica extracts on Atlantic salmon spermatozoa. Apoplastic extracts were used to determine ice recrystallization inhibition (IRI), thermal hysteresis (TH) activities and ice crystal morphology. Spermatozoa were cryopreserved using a standard cryoprotectant medium (C+) and three alternative media supplemented with apoplastic extracts. Flow cytometry was employed to measure plasma membrane integrity (PMI) and mitochondrial membrane potential (MMP) postthaw. Results showed that a low concentration of AFPs (0.05 mg/mL) provided significant IRI activity. Apoplastic extracts from D. antarctica demonstrated a cryoprotective effect on salmon spermatozoa, with PMI comparable to the standard medium. Moreover, samples treated with apoplastic extracts exhibited a higher percentage of cells with high MMP. These findings represent the first and preliminary report that suggests that AFPs derived from apoplastic extracts of D. antarctica have the potential to serve as cryoprotectants and could allow the development of novel freezing media.

Post-thaw quality assessment of testicular fragments as a source of spermatogonial cells for surrogate production in the flatfish Solea senegalensis

Cryopreservation of germ cells would facilitate the availability of cells at any time allowing the selection of donors and maintaining quality control for further applications such as transplantation and germline recovery. In the present study, we analyzed the efficiency of four cryopreservation protocols applied either to isolated cell suspensions or to testes fragments from Senegalese sole. In testes fragments, the quality of cryopreserved germ cells was analyzed in vitro in terms of cell recovery, integrity and viability, DNA integrity (fragmentation and apoptosis), and lipid peroxidation (malondialdehyde levels). Transplantation of cryopreserved germ cells was performed to check the capacity of cells to in vivo incorporate into the gonadal primordium of Senegalese sole early larval stages (6 days after hatching (dah), pelagic live), during metamorphosis (10 dah) and at post-metamorphic stages (16 dah and 20 dah, benthonic life). Protocols incorporating dimethyl sulfoxide (DMSO) as a cryoprotectant showed higher number of recovered spermatogonia, especially in samples cryopreserved with L-15 + DMSO (0.39 ± 0.18 × 106 cells). Lipid peroxidation and DNA fragmentation were also significantly lower in this treatment compared with other treatments. An important increase in oxidation (MDA levels) was detected in samples containing glycerol as a cryoprotectant, reflected also in terms of DNA damage. Transplantation of L-15 + DMSO cryopreserved germ cells into larvae during early metamorphosis (10 dah, 5.2 mm) showed higher incorporation of cells (27.30 ± 5.27%) than other larval stages (lower than 11%). Cryopreservation of germ cells using testes fragments frozen with L-15 + DMSO was demonstrated to be a useful technique to store Senegalese sole germline.

Oxidative Stress and DNA Fragmentation in Frozen/Thawed Common Carp Cyprinus carpio Sperm With and Without Supplemental Proteins

Using cryopreservation techniques can increase the effectiveness of reproducing cultured fish species by ensuring a dependable supply of sperm, although the quality of the sperm could be impacted by the procedures involved. The goal of this study was to investigate the effect of purified seminal plasma transferrin (Tf), bovine serum albumin (BSA), and antifreeze protein (AFP) types I and III at 1 µg mL^-1 on relevant characteristics of cryopreserved sperm from common carp Cyprinus carpio. We compared oxidative stress indices, antioxidant activity, and DNA fragmentation of fresh sperm to that frozen with extender only or with Tf, BSA, or AFP types I and III. Fresh sperm had significantly lower levels of thiobarbituric acid reactive substances (TBARS) compared to samples that underwent cryopreservation without protein treatment, which resulted in 0.54 ± 0.06 nmol/10⁸ cells of TBARS. Carbonyl derivatives of proteins (CP) decreased significantly (ANOVA; P > 0.05) in carp sperm with addition of Tf, AFPI, and AFPIII. Significant differences in superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) activity were seen in sperm supplemented with Tf, BSA, AFPI, and AFPIII from those without. Significantly less DNA damage, expressed as percent tail DNA (11.56 ± 1.34) and olive tail moment (0.59 ± 0.13), was recorded in samples cryopreserved with Tf. The findings indicated that addition of Tf, BSA, AFPI, or AFPIII to cryopreservation medium is beneficial to sperm preservation. The mechanisms through which these proteins act positively on sperm need to be further investigated.

Effects of Antifreeze Protein Type I and Glycerol in Diluents on Cryopreserved Goat Epididymal Sperm

The effect of antifreeze protein (AFP) as a cryoprotectant used in different concentrations of glycerol on post-thaw quality of epididymal sperm was investigated. Sperm were isolated from 50 testicles, obtained from 25 healthy mature goat bucks, with progressive motility >80%, and total morphological abnormalities <10% were pooled in each replication. The semen samples were diluted with Tris-citrate-fructose-soybean lecithin extender containing different concentration of AFP [0 μg/mL (A0), 5 μg/mL (A5), 10 μg/mL (A10)]. Each concentration of AFP was added in an extender containing either 7% (G7) or 5% (G5) glycerol. Post-thaw total and progressive motility were found to be higher (p < 0.05) in groups A5G5 and A5G7. Plasma membrane integrity, sperm acrosome integrity, DNA integrity, acrosome intact sperm, and mitochondrial membrane potential were found to be higher (p < 0.05) in groups A5G5 and A10G5. Sperm viability was found to be higher (p < 0.05) in group A5G5, while lipid peroxidation was recorded lower (p < 0.05) in groups A5G5 and A5G7. Regarding the apoptosis occurrence, the results demonstrate higher (p < 0.05) live post-thawed spermatozoa for groups containing 5 μg/mL AFP with 5% and 7% glycerol in addition to the lowest (p < 0.05) value for groups containing 0 μg/mL AFP with 5% and 7% glycerol. Based on these results, the present study concludes that the addition of 5 μg/mL AFP in combination with 5% glycerol in freezing extender improves the post-thaw quality, structure, and function parameters for buck spermatozoa.

Effect of antifreeze protein type III on frozen/thawed of spermatozoa recover from goat epididymis

The objective of this study was to evaluate the effect of antifreeze protein type III (AFP III) on the freezing of epididymal spermatozoa of goats. A total of 16 pairs of testicles were collected in a slaughterhouse and transported at approximately 5 °C in a thermal box. Epididymal spermatozoa were recovered by retrograde lavage and evaluated using a phase contrast microscope. Then, they were cryopreserved in extender based on Tris-egg yolk, supplemented with AFP III (0, 1, 10, 100 μg/mL), using an automated system. After thawing (37 °C/30 s), the spermatozoa kinetics were evaluated using the CASA automated system; and plasma and acrosome membrane integrity, mitochondrial membrane potential, and intracellular ROS production, by flow cytometry. There was no difference (P ≥ 0.05) between the experimental groups for the parameters of spermatozoa kinetics, mitochondrial membrane potential, and ROS production. However, the integrity of plasma and acrosome membranes of frozen spermatozoa with 100 μg/mL of AFP III was lower (P < 0.05) than the control group. It was concluded that the addition of AFP III to the Tris-egg yolk extender, used in the freezing of sperm obtained from the epididymis of goats, did not improve the preservation of these cells.

Regulation of semen quality by fatty acids in diets, extender, and semen

Fatty acids (FAs) are classified into different types according to the degree of hydrocarbon chain saturation, including saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), omega-3 polyunsaturated fatty acids (omega-3 PUFAs) and omega-6 polyunsaturated fatty acids (omega-6 PUFAs), which play an important role in maintaining semen quality. This review focuses on the regulation of FAs in semen, diet and extender on semen quality, and expounds its effects on sperm motility, plasma membrane integrity, DNA integrity, hormone content, and antioxidant capacity. It can be concluded that there are species differences in the FAs profile and requirements in sperm, and their ability to regulate semen quality is also affected by the addition methods or dosages. Future research directions should focus on analyzing the FAs profiles of different species or different periods of the same species and exploring suitable addition methods, doses and mechanism of regulating semen quality.

RhoA improves cryopreservation of rooster sperm through the Rho/RhoA-associated Kinase/cofilin pathway

Cryopreservation of rooster sperm leads to relatively low semen quality due to cytoskeletal damage during the freeze-thawing process. This study aimed to explore how the addition of RhoA recombinant protein affected the viability and subcellular structure of rooster sperm after freeze-thawing and elucidated the molecular mechanisms of sperm cryopreservation. Semen quality and acrosome integrity testing revealed that the addition of 0.5 μg/mL RhoA recombinant protein to the cryoprotectant fluid significantly increased sperm motility, survival rate, linearity, straight-line velocity, and acrosome integrity after freeze-thawing (P < 0.05). Ultrastructure analysis of cryopreserved sperm showed structural damage to the sperm plasma membrane, nuclear membrane, and tail. However, compared to the control, these structural changes were reduced upon the addition of RhoA recombinant protein to the cryoprotective fluid (P < 0.05). Western blotting revealed that the expression of Rho/RhoA-associated kinase and p-cofilin was increased, and cofilin expression was decreased after sperm cryopreservation with recombinant RhoA protein. Treatment with Y-27632, a ROCK antagonist, suppressed ROCK and p-cofilin expression and decreased semen quality, acrosome integrity, and ultrastructure integrity. In summary, we have demonstrated a cryoprotective effect in spermatozoa involving the Rho/ROCK pathway during freeze-thawing. Furthermore, the addition of 0.5 μg/mL RhoA recombinant protein to the cryoprotective fluid improved rooster semen quality and subcellular structural homeostasis after freeze-thawing via the Rho/ROCK pathway. This pathway may regulate the dynamic reorganization of the actin cytoskeleton by regulating the cofilin phosphorylation.

miR-199-5p regulates spermiogenesis at the posttranscriptional level via targeting Tekt1 in allotriploid crucian carp

BACKGROUND

Sperm abnormalities are one of the primary factors leading to male sterility, but their pathogenesis is still unclear. Although miRNAs are suggested to exert important roles in the regulation of spermatogenesis at both transcriptional and posttranscriptional levels, little is currently known regarding the regulation of sperm flagella assembly by microRNAs (miRNAs). The role of miRNAs in the development of sperm abnormalities in sterile triploid fish has not been studied.

RESULTS

In this study, we found that miR-199-5p was widely expressed in all detected tissues of different-ploidy crucian carp. As one of the testis-specific candidate markers, Tekt1 was predominantly expressed in the testis. Quantitative real-time PCR (qRT-PCR) analyses showed that the expression trend of miR-199-5p was exactly opposite to that of Tekt1. Through bioinformatics analysis, we identified a putative miR-199-5p binding site in the Tekt1 mRNA. We further identified Tekt1 as a target of miR-199-5p using luciferase reporter assay. Finally, we confirmed that miR-199-5p was necessary for sperm flagellar assembly and spermatogenesis in vivo via intraperitoneal injection of miR-199-5p antagomir or agomir in diploid red crucian carp. Moreover, miR-199-5p gain-of-function could lead to spermatids apoptosis and abnormal spermatozoa structure, which is similar to that of allotriploid crucian carp.

CONCLUSIONS

Our studies suggested that abnormally elevated miR-199-5p inhibited the sperm flagella formation in spermiogenesis by negatively regulating the expression of Tekt1, thereby causing sperm abnormalities of male allotriploid crucian carp.

Ex vivo exposure to titanium dioxide and silver nanoparticles mildly affect sperm of gilthead seabream (Sparus aurata) - A multiparameter spermiotoxicity approach

Nanoparticles (NP) are potentially reprotoxic, which may compromise the success of populations. However, the reprotoxicity of NP is still scarcely addressed in marine fish. Therefore, we evaluated the impacts of environmentally relevant and supra environmental concentrations of titanium dioxide (TiO₂: 10 to 10,000 μg·L^-1) and silver NP (Ag: 0.25 to 250 μg·L^-1) on the sperm of gilthead seabream (Sparus aurata). We performed short-term direct exposures (ex vivo) and evaluated sperm motility, head morphometry, mitochondrial function, antioxidant responses and DNA integrity. No alteration in sperm motility (except for supra environmental Ag NP concentration), head morphometry, mitochondrial function, and DNA integrity occurred. However, depletion of all antioxidants occurred after exposure to TiO₂ NP, whereas SOD decreased after exposure to Ag NP (lowest and intermediate concentration). Considering our results, the decrease in antioxidants did not indicate vulnerability towards oxidative stress. TiO₂ NP and Ag NP induced low spermiotoxicity, without proven relevant ecological impacts.

Antifreeze proteins for low-temperature preservation in reproductive medicine: A systematic review over the last three decades

Antifreeze proteins (AFPs) are synthesized by diverse non-mammalian species, allowing them to survive in severely cold environments. Since the 1990s, the scientific literature reports their use for low-temperature preservation of germplasm. The aim of this systematic review was to compile available scientific evidence regarding the use of AFP for low-temperature preservation of several reproductive specimens. Internet databases were consulted using the terms: "antifreeze protein" OR "AFP" OR "antifreeze glycoprotein" OR "AFGP" OR "ice-binding protein" OR "IBP" OR "thermal hysteresis protein" AND "cryopreservation". From 56 articles, 87 experiments testing AFPs in low-temperature preservation of gametes, embryos or reproductive tissues/cells were fully analyzed and outcomes were annotated. A positive outcome was considered as a statistically significant improvement on any parameter evaluated after low-temperature preservation with AFP, whereas a negative outcome included worsening of any evaluated parameter, in comparison to untreated groups or groups treated with a lower concentration of AFP. The findings indicated that research on the use of AFP as a cryoprotectant for reproductive specimens has increased markedly over the past decade. Some experiments reported both positive and negative results, which depended, on AFP concentration in the preservation media. Variation in the outcomes associated with species was also observed. Among the 66 experiments conducted in mammals, 77.3% resulted in positive, and 28.8% in negative outcomes after the use of AFP. In fishes, positive and negative outcomes were observed in 71.4% and 33.3% of 21 experiments, respectively. Most positive outcomes included preserving cell post-warming survival. The beneficial effect of AFP supports its use in cryobiological approaches used in human and veterinary medicines and animal protein industry. Moreover, combination of different AFP types, or AFP with antioxidants, or even the use of AFP-biosimilar, comprise some promising approaches to be further explored in cryopreservation.

Spotted Wolffish Broodstock Management and Egg Production: Retrospective, Current Status, and Research Priorities

The first artificially fertilized spotted wolffish (Anarhichas minor) eggs hatched in Norway in the mid-1990s as this species was considered by Norwegian authorities to be a top candidate species for cold-water aquaculture in the North Atlantic regions. Previous research conducted in Norway (since 1992) and Canada (since 2000), focused on identifying key biological parameters for spotted wolffish cultivation which led, respectively, to the rapid establishment of a full commercial production line in northern Norway, while Québec (Canada) is witnessing its first privately driven initiative to establish commercial production of spotted wolffish on its territory. The control of reproduction can be viewed as a major requirement to achieve the development of performant strains using genetic selection tools and/or all-year-round production to bring about maximal productivity and synchronization among a given captive population. Although the basic reproduction aspects are more understood and controlled there are still some challenges remaining involving broodstock and upscaling of operations that limit the achievement of a standardized production at the commercial level. Quality of gametes is still considered a major constraint and it can be affected by multiple factors including nutrition, environmental conditions, handling practices, and welfare status. Internal insemination/fertilization and the protracted incubation period are challenging as well as the establishment of a health monitoring program to secure large-scale operations. The profound progress achieved in the control of reproduction, sperm handling, and cryopreservation methods for this species is presented and discussed. In this review, we also go into detail over the full range of up-to-date cultivation practices involving broodstock and identify areas that could benefit from additional research efforts (i.e., broodstock nutrition, health and welfare, scaling-up egg and larval production, genetics, and development of selective breeding programs).

Type III antifreeze protein (AFP) improves the post-thaw quality and in vivo fertility of rooster spermatozoa

Antifreeze proteins (AFP) have the potential for improving sperm cryopreservation. We have applied Type III antifreeze protein (AFP3) on the cryopreservation of spermatozoa from broiler breeder roosters, aiming to enhance post-thawing quality and fertility. Semen was extended at 37°C in Lake's extender containing AFP3 at 0.01, 0.1, 1, 5, and 10 µg/mL (no AFP3 as control). Post-thawing sperm assessment included sperm motility (CASA), morphology, membrane functionality by hypoosmotic swelling test (HOST), lipoperoxidation as malondialdehyde (MDA) production, and sperm viability, early apoptosis (phosphatidylserine exposure as annexin V-positive staining in viable spermatozoa), and mitochondrial activity by flow cytometry. Fertility was assessed after artificial insemination (30 hens/treatment). Total and progressive motility, membrane functionality, and mitochondrial activity increased in 0.1 and 1 µg/mL AFP, compared to control and other concentrations, whereas apoptosis was significantly lower. VAP, VSL, and viability were significantly higher for 1 µg/mL AFP3 than with the other treatments except for 0.1 µg/mL (which was not always significantly different from the control or other concentrations), and with abnormal forms being significantly lower. The proportion of fertilized and hatched eggs was also higher for 1 µg/mL AFP3, with 0.1 µg/mL also showing significantly higher results than the control, and no differences with other concentrations). In conclusion, 1 µg/mL AFP3 could improve the post-thawing results of rooster spermatozoa frozen in Lake's extender. According to our results, concentrations between 1 and 0.1 µg/mL could be similarly efficient.

Effects of Antifreeze Protein III on Sperm Cryopreservation of Pacific Abalone, Haliotis discus hannai

Pacific abalone (Haliotis discus hannai) is a highly commercial seafood in Southeast Asia. The aim of the present study was to improve the sperm cryopreservation technique for this valuable species using an antifreeze protein III (AFPIII). Post-thaw sperm quality parameters including motility, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, fertility, hatchability, and mRNA abundance level of heat shock protein 90 (HSP90) were determined to ensure improvement of the cryopreservation technique. Post-thaw motility of sperm cryopreserved with AFPIII at 10 µg/mL combined with 8% dimethyl sulfoxide (DMSO) (61.3 ± 2.7%), 8% ethylene glycol (EG) (54.3 ± 3.3%), 6% propylene glycol (PG) (36.6 ± 2.6%), or 2% glycerol (GLY) (51.7 ± 3.0%) was significantly improved than that of sperm cryopreserved without AFPIII. Post-thaw motility of sperm cryopreserved with 2% MeOH and 1 µg/mL of AFPIII was also improved than that of sperm cryopreserved without AFPIII. A combination of 10 µg/mL AFPIII with 8% DMSO resulted in the highest post-thaw motility, showing AI of 60.1 ± 3.9%, PMI of 67.2 ± 4.0%, and MMP of 59.1 ± 4.3%. DNA integrity of sperm cryopreserved using 10 µg/mL AFPIII combined with 8% DMSO was not significantly (p > 0.05) different from that of fresh sperm. Cryopreservation using a combination of AFPIII with 8% DMSO improved fertilization and hatching rates of sperm compared to that of cryopreservation without supplementation of 10 µg/mL AFPIII. Sperm cryopreserved using AFPIII showed higher mRNA abundance levels of HSP90 than those cryopreserved without AFPIII. Results of the present study suggest that 10 µg/mL AFPIII combined with 8% DMSO can be used for large scale cryopreservation of Pacific abalone sperm and for hatchery production.

The Effects of Antifreeze Protein III Supplementation on the Cryosurvival of Goat Spermatozoa During Cryopreservation

Antifreeze protein (AFP) has been shown to have beneficial effects on frozen mammalian spermatozoa. However, rare reports have been published regarding the use of AFPs in storage of goat spermatozoa. The aim of this study was to investigate the effects of AFPIII on the quality of goat semen during cryopreservation. Ejaculates were collected from six Yunshang black goats through an artificial vagina. The collected semen was pooled, divided into five aliquots, and diluted with the commercial bull semen extender containing: no AFPIII (AFP-0, control), 1 μg/mL AFPIII (AFP-1), 10 μg/mL AFPIII (AFP-10), 50 μg/mL AFPIII (AFP-50), and 100 μg/mL AFPIII (AFP-100), respectively. Spermatozoa motility, membrane integrity, acrosome integrity, mitochondrial function, distribution of phosphatidylserine, and formation of reactive oxygen species (ROS) were measured after the freezing and thawing process. The results showed that the spermatozoa motility, membrane integrity, acrosome integrity, and mitochondrial function were significantly higher in frozen spermatozoa using the extender containing 1 μg/mL AFPIII as compared with the other groups (p < 0.05). Furthermore, the extender supplemented with 1 μg/mL of AFPIII resulted in higher viable and lower nonviable spermatozoa compared with the other treated groups (p < 0.05), after staining using Annexin V-fluoresceine isothiocyanate (Annexin V-FITC) and Propidium Iodide. No significant differences were found between these groups in relation to viable cells with lower ROS production. In conclusion, the addition of AFPIII to the freezing extender improved the post-thaw quality of goat semen. The optimal concentration used in this study was 1 μg/mL. However, excessively high concentrations of AFPIII were unable to exhibit their cryoprotective effects on goat spermatozoa. However, the presence of AFPIII cannot mitigate oxidative stress caused by the freezing and thawing process. In addition, in vitro fertilization or artificial insemination can further evaluate the effects of AFPIII on frozen-thawed goat spermatozoa.

Effect of exogenous lipids on cryotolerance of Atlantic salmon (Salmo salar) spermatozoa

The development of semen cryopreservation strategies is necessary to improve the semen storage technologies of species of great commercial interest for aquaculture. Recent studies demonstrate that lipids play an important role in the fertility and cryotolerance of fish gametes. This study investigated the effect of exogenous lipids in the freezing medium on the post-thaw functional parameters of Salmo salar spermatozoa. Semen samples (n = 12) were incubated in standard extender supplemented with different concentrations of oleic acid (OA, C18:1n9), linoleic acid (LA, C18:2n6), arachidonic acid (ARA, C20:4n6) and cholesterol-loaded cyclodextrin (CLC). Post-thaw motility, membrane integrity, mitochondrial membrane potential (ΔΨm), superoxide anion (O₂^•-) and fertility rates were analyzed. The results revealed that the semen incubated with 0.003 mmol/L OA increased the motility (~7%) and ΔΨm (~2%) (P < 0.05), but membrane integrity and fertility were not increased. The addition of 0.003 mmol/L LA increased the motility (~4%) and all LA extenders increased the ΔΨm (P < 0.05); however, LA increased the O₂^•- levels and decreased the membrane integrity and fertility (P < 0.05). Semen incubated with ARA improved sperm motility (~5%), membrane integrity (~10.5%) and fertility rates (~11%) (P < 0.05). The maximum improvement in post-thaw sperm functionality was observed by adding 0.003 mmol/L ARA. In contrast, sperm quality parameters and fertility were decreased by the CLC addition (P < 0.05). This study showed that ARA could be considered as an additive for semen cryopreservation and could be relevant in the reproductive process and reproductive management of Salmo salar.

Supplementation of exogenous lipids via liposomes improves coral larvae settlement post-cryopreservation and nano-laser warming

Coral reefs worldwide are receding because of detrimental human activities, and cryopreservation of coral larvae would ensure that their genetic biodiversity is not irremediably lost. In recent years, the vitrification and laser warming of coral propagules has demonstrated promising results. During cryopreservation, cellular membranes undergo substantial reconfigurations that may affect survival. Fat enrichment may alter the physical proprieties of cell membranes and improve resistance to low temperatures. Therefore, the aim of this study was to determine whether supplementation of exogenous lipids using liposomes would improve cryosurvival and further development of the vitrified and laser-warmed coral larvae of Seriatopora caliendrum and Pocillopora verrucosa. A vitrification solution (VS) composed of 2 M ethylene glycol (EG), 1 M propylene glycol (PG), 40% (w/v) Ficoll, and 10% gold nanoparticles (at a final concentration of 1.2 × 10¹⁸ particles/m³ and an optimised emission wavelength of 535 nm) was chosen. Coral larvae were subjected to vitrification with VS incorporating one of four lipid classes: phosphatidylcholine (PC), phosphatidylethanolamine (PE), erucic acid (EA), and linoleic acid (LA). Warming was achieved using a single laser pulse (300 V, 10 ms pulse width, 2 mm laser beam diameter). A significantly higher vitality rate was observed in S. caliendrum larvae subjected to vitrification and laser warming with EA-incorporated VS, and P. verrucosa larvae vitrified and laser warmed using PE-incorporated VS achieved a significantly higher settlement rate. Our study demonstrated that supplementation of exogenous lipids with liposomes enhances coral larvae cryotolerance and improves cryopreservation outcomes. Lipid enrichment may play a key role in cryobanking coral propagules, and in propagule development after thawing.

Addition of antifreeze protein type I or III to extenders for ram sperm cryopreservation

Antifreeze proteins (AFP) play an important role in cellular survival at sub-zero temperatures. This study assessed the effect of AFP type I or III in semen extender (TRIS-egg yolk) for ram sperm cryopreservation. Pooled semen of four rams were allocated into five treatments: Control (CONT, without AFP); AFP Type I [0.1 (AFPI-0.1) or 0.5 (AFPI-0.5) μg/mL]; or III [0.1 (AFPIII-0.1) or 0.5 (AFPIII-0.5) μg/mL], and then frozen in six replicates. Treatments affected kinetic parameters, plasma membrane integrity and morphology (P < 0.05). The AFPIII-0.1 presented lesser total motility. Linearity was greater in AFPI-0.1, AFPI-0.5 and AFPIII-0.5 and straightness was greater in all AFP-supplemented extenders. Plasma membrane integrity was greater in AFPI-0.1 and AFPI-0.5. All AFP groups had greater percentage of normal sperm than CONT. No differences (P > 0.05) were observed in hypoosmotic test, sperm acrosome status, mitochondrial activity, chromatin condensation, perivitelline membrane binding rate and lipoperoxidation. In conclusion, the use of AFP, predominantly type I, may increase sperm cell protection during cryopreservation, with no adverse effect on potential fertilization capacity or increase in reactive oxygen species, being a potential cryoprotectant to ram sperm.

Dimethyl sulfoxide: a central player since the dawn of cryobiology, is efficacy balanced by toxicity?

Dimethyl sulfoxide (DMSO) is the cryoprotectant of choice for most animal cell systems since the early history of cryopreservation. It has been used for decades in many thousands of cell transplants. These treatments would not have taken place without suitable sources of DMSO that enabled stable and safe storage of bone marrow and blood cells until needed for transfusion. Nevertheless, its effects on cell biology and apparent toxicity in patients have been an ongoing topic of debate, driving the search for less cytotoxic cryoprotectants. This review seeks to place the toxicity of DMSO in context of its effectiveness. It will also consider means of reducing its toxic effects, the alternatives to its use and their readiness for active use in clinical settings.

Sperm Lipid Composition in Early Diverged Fish Species: Internal vs. External Mode of Fertilization

The lipid composition of sperm membranes is crucial for fertilization and differs among species. As the evolution of internal fertilization modes in fishes is not understood, a comparative study of the sperm lipid composition in freshwater representatives of externally and internally fertilizing fishes is needed for a better understanding of taxa-specific relationships between the lipid composition of the sperm membrane and the sperm physiology. The lipidomes of spermatozoa from stingray, a representative of cartilaginous fishes possessing internal fertilization, and sterlet, a representative of chondrostean fishes with external fertilization, have been studied by means of nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), electrospray MS, gas chromatography-(GC) MS, and thin-layer chromatography (TLC). NMR experiments revealed higher cholesterol content and the presence of phosphatidylserine in stingray compared to sterlet sperm. Unknown MS signals could be assigned to different glycosphingolipids in sterlet (neutral glycosphingolipid Gal-Cer(d18:1/16:0)) and stingray (acidic glycosphingolipid sulpho-Gal-Cer(d18:1/16:0)). Free fatty acids in sterlet sperm indicate internal energy storage. GC-MS experiments indicated a significant amount of adrenic acid, but only a low amount of docosahexaenoic acid in stingray sperm. In a nutshell, this study provides novel data on sperm lipid composition for freshwater stingray and sterlet possessing different modes of fertilization.

The Use of Antifreeze Proteins in the Cryopreservation of Gametes and Embryos

The cryopreservation of gametes and embryos is a technique widely used in reproductive biology. This technology helps in the reproductive management of domesticated animals, and it is an important tool for gene banking and for human-assisted reproductive technologies. Antifreeze proteins are naturally present in several organisms exposed to subzero temperatures. The ability for these proteins to inhibit ice recrystallization together with their ability to interact with biological membranes makes them interesting molecules to be used in cryopreservation protocols. This mini-review provides a general overview about the use of antifreeze proteins to improve the short and long term storage of gametes and embryos.

Effect of polyvinyl alcohol on survival and function of angora buck spermatozoa following cryopreservation

The aim of this study was to examine effects of polyvinyl alcohol (PVA) on buck semen quality. Seventy-five ejaculates were collected and diluted in Tris-egg yolk extender containing one of three PVA co-polymers of 9, 18 and 100 kDa. Five different concentrations 0.001, 0.01, 0.1, 1 and 2% of the PVA co-polymers were added to the extender with respected to the decreasing glycerol concentrations of 5, 4, 3, 3, 2% respectively. Following freeze-thaw, sperm motility, viability, acrosome-intact spermatozoa and mitochondrial membrane potentials were analysed. During freezing, sperm seeding temperature were recorded with a cryo-thermometer. PVA 2% glycerol group gained 8.2 ± 1 °C latent heat plateau difference comparing to control. Highest motility was found in PVA 18 kDa with regardless of the dosage (P < 0.001). All PVA copolymers gained higher motility independently in all other dosage groups (except PVA 2%) comparing to control (P < 0.001). Live spermatozoa rate between treatment groups were statistically insignificant (P = 0.953), however, when moribund sperm were gated out PVA 9 induced better protection with respect to other groups (P < 0.05). Intact acrosome rate was statically higher in PVA groups (P < 0.002) and subgroups (P < 0.001). Mitochondrial membrane potential was higher in all experimental groups comparing to control group (P < 0.001). PVA co-polymer concentrations of 0.01, 0.1, 1 and 2% v/v (PBS: PVA) decreased the concentration of glycerol required for freezing in a 100 ml volume by 0, 1, 2, 2, and 3% v/v from the control dose (5%), respectively. In conclusion, synthetic PVA-derived ice blocking agents offer new opportunities for improving the post-thaw buck sperm quality.

Swimming at different temperatures: The lipid composition of sperm from three freshwater fish species determined by mass spectrometry and nuclear magnetic resonance spectroscopy

The spawning behavior of different fish species is as diverse as their habitats. A lot of factors influence the (phospho)lipid composition of fish sperm, including the water temperature at which spawning takes place. Therefore, this study aimed on the elucidation of the phospholipid composition of sperm from three fish species from different orders (common carp - Cyprinus carpio, northern pike - Esox lucius and burbot - Lota lota) with different spawning temperatures by nuclear magnetic resonance spectroscopy (NMR), matrix-assisted laser desorption/ionization mass spectrometry and thin-layer chromatography (TLC) coupled to electrospray ionization mass spectrometry as well as gas chromatography. Next to the lipid composition that was different for carp, northern pike and burbot, regarding the moieties of the different (phospho)lipid classes (particularly sphingomyelin and acidic phospholipids) and the saturation degree of the fatty acyl residues, there were differences observed depending on the analytical method that was used. The results from TLC and NMR investigations differed regarding the amounts of the different phospholipids. Reasons for these discrepancies are discussed in detail.

Seminal plasma transferrin effects on cryopreserved common carp Cyprinus carpio sperm and comparison with bovine serum albumin and antifreeze proteins

In the current study, there was evaluation of the cryopreservation effectiveness of common carp Cyprinus carpio sperm when cryopreservation medium was supplemented with proteins. Semen was diluted with Kurokura's extender composing 180 mM NaCl, 2.68 mM KCl, 1.36 mM CaCl₂, 2.38 mM NaHCO₃, and 10% dimethylsulfoxide (DMSO). Cryopreservation medium was supplemented with purified seminal plasma transferrin (Tf), bovine serum albumin (BSA) or antifreeze protein (AFP) Types I and III. Concentration of proteins evaluated was 0.1 μg/ml, 1 μg/ml, and 10 μg/ml. Motility and curvilinear velocity of spermatozoa was evaluated by the Computer Assisted Semen Analyzer (CASA). The percent of motile cells and spermatozoa curvilinear velocity of frozen-thawed sperm with supplementation of Tf and AFP III at all concentrations were greater compared to samples with no added proteins. The protective effect of BSA and AFP I was less and dose-dependent. Thus, it is concluded that incorporation of Tf in the extender before freezing improves crypreservation of common carp spermatozoa whereas supplementation with AFP III in greater concentrations was more effective.

Human leukemia cells (HL-60) proteomic and biological signatures underpinning cryo-damage are differentially modulated by novel cryo-additives

BACKGROUND

Cryopreservation is a routinely used methodology for prolonged storage of viable cells. The use of cryo-protective agents (CPAs) such as dimethylsulfoxide (DMSO), glycerol, or trehalose is paramount to reducing cellular cryo-injury, but their effectiveness is still limited. The current study focuses on establishing and modulating the proteomic and the corresponding biological profiles associated with the cryo-injury of human leukemia (HL-60) cells cryopreserved in DMSO alone or DMSO +/- novel CPAs (e.g., nigerose [Nig] or salidroside [Sal]).

FINDINGS

To reduce cryo-damage, HL-60 cells were cultured prior and post cryopreservation in malondialdehyde Roswell Park Memorial Institute medium-1640 media +/- Nig or Sal. Shotgun proteomic analysis showed significant alterations in the levels of proteins in cells cryopreserved in Nig or Sal compared to DMSO. Nig mostly affected cellular metabolism and energy pathways, whereas Sal increased the levels of proteins associated with DNA repair/duplication, RNA transcription, and cell proliferation. Validation testing showed that the proteome profile associated with Sal was correlated with a 2.8-fold increase in cell proliferative rate. At the functional level, both Nig and Sal increased glutathione reductase (0.0012±6.19E-05 and 0.0016±3.04E-05 mU/mL, respectively) compared to DMSO controls (0.0003±3.7E-05 mU/mL) and reduced cytotoxicity by decreasing lactate dehydrogenase activities (from -2.5 to -4.75 fold) and lipid oxidation (-1.6 fold). In contrast, only Nig attenuated protein carbonylation or oxidation.

CONCLUSIONS

We have identified key molecules and corresponding functional pathways underpinning the effect of cryopreservation (+/- CPAs) of HL-60 cells. We also validated the proteomic findings by identifying the corresponding biological profiles associated with promoting an anti-oxidative environment post cryopreservation. Nig or Sal in comparison to DMSO showed differential or additive effects in regard to reducing cryo-injury and enhancing cell survival/proliferation post thaw. These results can provide useful insight to cryo-damage and the design of enhanced cryomedia formulation.

Ice recrystallization is strongly inhibited when antifreeze proteins bind to multiple ice planes

Ice recrystallization is a phenomenon observed as the increase in ice crystal size within an already frozen material. Antifreeze proteins (AFPs), a class of proteins capable of arresting ice crystal growth, are known to inhibit this phenomenon even at sub milli-molar concentrations. A tremendous range in the possible applications of AFPs is hence expected in both medical and industrial fields, while a key determinant of the ice recrystallization inhibition (IRI) is hardly understood. Here, IRI efficiency and ice plane affinity were examined for the wild-type AFPI–III, a defective AFPIII isoform, and a fungal AFP isoform. To simplify the IRI analysis using the formal representation of Ostwald-ripening (r³ = r₀³ + kt), we monitored specific ice grains exhibiting only uniform growth, for which maximum Feret diameter was measured. The cube of an ice grain’s radius (r³) increased proportionately with time (t), and its slope gave the recrystallization rate (k). There was a significant difference in the IRI efficiency between the samples, and the fungal AFP possessing the activity with the smallest amount (0.27 μM) exhibited an affinity to multiple ice planes. These results suggest that the IRI efficiency is maximized when AFPs bind to a whole set of ice planes.

Protective role of antifreeze proteins on sterlet (Acipenser ruthenus) sperm during cryopreservation

The loss of sperm quality in sterlet (Acipenser ruthenus) due to freeze-thaw process in cryopreservation was investigated in the present study. Two antifreeze proteins (AFPI or AFPIII) were used at different concentrations of 0.1, 1, 10, and 100 μg/mL. We compared motility, curvilinear velocity, and plasma membrane integrity of fresh, cryopreserved sperm, and sperm cryopreserved in the presence of antifreeze proteins. Fresh sperm (control) had 85 ± 4% motility and 160 ± 2 μm/s curvilinear velocity, respectively. After cryopreservation, the motility of frozen-thawed sperm without addition of antifreeze proteins significantly decreased (44 ± 9%), compared to the control. The highest motility of frozen-thawed sperm was obtained in cryopreserved sperm with addition of 1 μg/mL of AFPIII (58 ± 14%). No significant differences were observed in curvilinear velocity between fresh sperm and cryopreserved sperm with/without addition of AFPI or AFPIII. The flow cytometry analysis revealed that fresh sperm contained 94.5 ± 6% live cells, while the cryopreserved sperm only contained 26.6 ± 14% live cells. Supplementation of antifreeze proteins has significantly improved the percentage of live cells in frozen-thawed sperm, except 0.1 μg/ml of AFPI group. No significant difference in percentage of live cells was detected in the sperm cryopreserved with 10 μg/mL of AFPI or AFPIII, compared to fresh sperm. Thus, addition of antifreeze proteins to cryopreservation medium could be considered to improve the post-thawed sperm quality of sterlet.

Effects of antifreeze proteins on cryopreserved sterlet (Acipenser ruthenus) sperm motility variables and fertilization capacity

The effect of antifreeze proteins on sterlet, Acipenser ruthenus sperm motility variables and fertilization rate were investigated after cryopreservation. Two types of antifreeze proteins (AFPI or AFPIII) were used at concentrations of 0.1, 1, 10 and 100 μg/mL. The motility variables of fresh and cryopreserved sperm with and without addition of antifreeze proteins were evaluated by the Computer Assisted Semen Analyzer (CASA). The fertilization rate using about 200,000 spermatozoa per egg was evaluated after 54 h incubation at 17 °C during the early stage of organogenesis. The motility, curvilinear velocity and straight-line velocity of fresh sperm was 93 ± 5%, 128 ± 13 μm/s and 89 ± 9 μm/s, respectively. There was a significant decrease of sperm motility rate between fresh sperm and cryopreserved sperm with/without addition of antifreeze proteins. The greatest motility among thawed samples was in the sperm cryopreserved with 10 μg/mL of AFPI (56 ± 20%), however, these data were not different compared to the sperm without antifreeze proteins (49 ± 14%). No statistical variations were detected in curvilinear velocity nor straight-line velocity. The fertilization rate with fresh sperm was 67 ± 7%. No significant differences were detected in fertilization rate between fresh and cryopreserved spermatozoa with/without addition of antifreeze proteins, except the sperm cryopreserved with 100 μg/mL of AFPIII (39 ± 14%). Thus, it is concluded that addition of antifreeze proteins to cryopreservation medium do not improve nor have toxicity effects on the quality and fertilization capacity of sterlet sperm after thawing.

Development of sea bream (Sparus aurata) semen vitrification protocols

The long-term goal of this research project is to set up efficient protocol that can be used to develop a standardized approach for vitrification of marine fish spermatozoa. In particular, the aim of the present study was to develop a vitrification protocol for sea bream (Sparus aurata) spermatozoa. To draw up the protocol, we tested two different dilution media (1% NaCl and Mounib medium), three different vitrification devices (loops, drops and cut straws), different cryoprotectants (CPs) and three different equilibration times (30, 60 and 120 s). The effect of the different vitrification procedures on spermatozoa quality was checked by measuring spermatozoa motility rate and viability, mitochondrial membrane potential and the fertilizing ability of both fresh and post-thawed gametes. The best result was obtained by dropping directly into liquid nitrogen 20 μl of spermatozoa suspension (drop-wise method) diluted with Mounib buffer containing 10% Me₂SO + 10% glycerol. The addition of a mixture of anti-freezing proteins, AFPI and AFPIII, to Mounib buffer significantly increases the spermatozoa quality following vitrification so confirming the usefulness of AFPs in improving the quality of gametes subjected to the vitrification process. The present study proves that vitrification offers an alternative to conventional sperm cryopreservation also in this species.

Applications of Antifreeze Proteins: Practical Use of the Quality Products from Japanese Fishes

Numerous embryonic ice crystals are generated in water at the moment of freezing. These crystals grow and merge together to form an ice block that can be generally observed. Antifreeze protein (AFP) is capable of binding to the embryonic ice crystals, inhibiting such an ice block formation. Fish-derived AFP additionally binds to membrane lipid bilayers to prolong the lifetime of cells. These unique abilities of AFP have been studied extensively for the development of advanced techniques, such as ice recrystallization inhibitors, freeze-tolerant gels, cell preservation fluids, and high-porosity ceramics, for which mass-preparation method of the quality product of AFP utilizing fish muscle homogenates made a significant contribution. In this chapter, we present both fundamental and advanced information of fish AFPs that have been especially discovered from mid-latitude sea area, which will provide a hint to develop more advanced techniques applicable in both medical and industrial fields.

Metabolic changes in droplet vitrified semen of wild endangered Persian sturgeon Acipenser persicus (Borodin, 1997)

Comparative quantitative metabolite profiling can be used for better understanding of cell functions and dysfunctions in particular circumstances such as sperm banking which is an important approach for cryopreservation of endangered species. Cryopreservation techniques have some deleterious effects on spermatozoa which put the obtained results in controversy. Therefore, in the present study, quantitative ¹H NMR (Nuclear Magnetic Resonance) based metabolite profiling was conducted to evaluate metabolite changes related to energetics and some other detected metabolites in vitrified semen of critically endangered wild Acipenser persicus. The semen was diluted with extenders containing 0, 5, 10, and 15 μM of fish antifreeze protein (AFP) type III as a cryoprotectant. Semen-extenders were vitrified and stored for two days. Based on post-thaw motility duration and motility percentage assessments, two treatments with 10 μM and 0 μM of AFP had the highest and the lowest motility percentages respectively and they were objected to ¹H NMR spectroscopy investigations in order to reveal the extremes of the metabolites dynamic range. Univariate (ANOVA) and multivariate (PCA) analysis of the resulting metabolic profiles indicated significant changes (P > 0.05) in metabolites. The level of some metabolites including acetate, adenine, creatine, creatine phosphate, lactate, betaine, sarcosine, β-alanine and trimethylamine N-oxide significantly decreased in vitrified semen while some others such as creatinine, guanidinoacetate, N, N-dimethylglycine, and glycine significantly increased. There were also significant differences between vitrified treatments in levels of creatine, creatine phosphate, creatinine, glucose, guanidinoacetate, lactate, N, N-dimethylglycine, and glycine, suggesting how fish AFP type III can be effective as a cryoprotectant.

Marine Antifreeze Proteins: Structure, Function, and Application to Cryopreservation as a Potential Cryoprotectant

Antifreeze proteins (AFPs) are biological antifreezes with unique properties, including thermal hysteresis(TH),ice recrystallization inhibition(IRI),and interaction with membranes and/or membrane proteins. These properties have been utilized in the preservation of biological samples at low temperatures. Here, we review the structure and function of marine-derived AFPs, including moderately active fish AFPs and hyperactive polar AFPs. We also survey previous and current reports of cryopreservation using AFPs. Cryopreserved biological samples are relatively diverse ranging from diatoms and reproductive cells to embryos and organs. Cryopreserved biological samples mainly originate from mammals. Most cryopreservation trials using marine-derived AFPs have demonstrated that addition of AFPs can improve post-thaw viability regardless of freezing method (slow-freezing or vitrification), storage temperature, and types of biological sample type.

Latent Ice Recrystallization Inhibition Activity in Nonantifreeze Proteins: Ca2+-Activated Plant Lectins and Cation-Activated Antimicrobial Peptides

Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of ice. These proteins have huge potential for use in cellular cryopreservation, ice-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting ice growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent ice recrystallization inhibition (IRI) activity. This IRI activity can be switched on/off by changing the Ca2+ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilic domains, rationalizing this choice. The cheap, and widely used, antimicrobial Nisin was found to have cation-dependent IRI activity, controlled by either acid or addition of histidine-binding ions such as zinc or nickel, which promote its amphipathic structure. These results demonstrate a new approach in the identification of antifreeze protein mimetic macromolecules and may help in the development of synthetic mimics of AFPs.

Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes?

BACKGROUND

In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART.

METHODS

A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented.

RESULTS AND CONCLUSIONS

New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo.

Efficiency of antifreeze glycoproteins for cryopreservation of Nili-Ravi (Bubalus bubalis) buffalo bull sperm

Experiments were conducted to evaluate the effect of Antarctic fish antifreeze glycoproteins, (AFGP) size 1-5 (34-10.5 kDa) and 7-8 (3.2 and 2.4 kDa) in extender on buffalo bull sperm at cooling (4 °C) and at post thawing. Semen was collected from three Nili-Ravi buffalo bulls with artificial vagina for 3 weeks. Qualifying ejaculates from each buffalo bull were diluted (at 37 °C having 50×10(6) sperm/mL) in tris-citric acid extender containing AFGP at 0 (control), 0.1, 1 and 10 μg/mL. An aliquot of diluted semen was evaluated for sperm progressive motility and plasma membrane integrity, while the remaining fraction was cooled to 4 °C in 2 h. Further, an aliquot of cooled semen was evaluated for the previously described variables and the remaining fraction was cryopreserved (-196 °C). After 24 h of storage, straws were thawed at 37 °C for 30 s to assess post-thaw sperm quality. Inclusion of AFGP in the extender did not affect (P>0.05) sperm progressive motility and plasma membrane integrity of buffalo bull sperm at cooling stage (4 °C). However, at post thawing, improvement (P<0.05) in sperm progressive motility and plasma membrane integrity was recorded in extender containing AFGP 1-5 and AFGP 7-8 at 1 μg/mL compared to the control. Percentage of live sperm with an intact acrosome remained similar (P>0.05) in extenders containing different amounts of AFGP and control. In conclusion, supplementation of 1 μg/ml of AFGP in extender improved the motility and plasma membrane integrity of Nili-Ravi buffalo sperm after thawing.

Experimental correlation between thermal hysteresis activity and the distance between antifreeze proteins on an ice surface

Temperature-controlled microfluidic devices and fluorescence microscopy illustrate the correlation between freezing-point depression and the distance between antifreeze proteins on an ice surface.

Detection of DNA damage caused by cryopreservation using a modified SCGE in large yellow croaker, Pseudosciaena crocea

We used single-cell gel electrophoresis (SCGE) to detect the integrity of sperm DNA of the teleost large yellow croaker, Pseudosciaena crocea, cryopreserved with Cortland solution and a range of 5% to 30% DMSO concentrations in order to test how sperm cryopreservation affected the DNA stability of nuclei. Electrophoresis was conducted for 60 min at 130 mA and 15 V. The comet images were analyzed with software CometScore 1.5, and parameters such as comet length, tail length and percentage DNA in the tail were obtained. Then the comet rate and damage coefficient were calculated. Results demonstrated that there were no significant differences in motility, comet rate and damage coefficient between fresh sperm and cryopreserved sperm stored in 5%, 10%, 15% and 20% DMSO, while the sperm cryopreserved with 25% and 30% DMSO had a lower motility, higher comet length and damage coefficients than those of fresh sperm. There was a positive correlation between comet rate of cryopreserved sperm and the concentration of DMSO. Our results demonstrate that toxicity of the cryoprotectant is the main cause of DNA damage in cryopreserved sperm nuclei.

Comparative proteome analysis of cryopreserved flagella and head plasma membrane proteins from sea bream spermatozoa: effect of antifreeze proteins

Cryopreservation induces injuries to fish spermatozoa that in turn affect sperm quality in terms of fertilization ability, motility, DNA and protein integrity and larval survival. To reduce the loss of sperm quality due to freezing-thawing, it is necessary to improve these procedures. In the present study we investigated the ability of two antifreeze proteins (AFPI and AFPIII) to reduce the loss of quality of sea bream spermatozoa due to cryopreservation. To do so, we compared viability, motility, straight-line velocity and curvilinear velocity of fresh and (AFPs)-cryopreserved spermatozoa. AFPIII addition to cryopreservation medium improved viability, motility and straight-line velocity with respect to DMSO or DMSO plus AFPI. To clarify the molecular mechanism(s) underlying these findings, the protein profile of two different cryopreserved sperm domains, flagella and head plasma membranes, was analysed. The protein profiles differed between fresh and frozen-thawed semen and results of the image analysis demonstrated that, after cryopreservation, out of 270 proteins 12 were decreased and 7 were increased in isolated flagella, and out of 150 proteins 6 showed a significant decrease and 4 showed a significant increase in head membranes. Mass spectrometry analysis identified 6 proteins (4 from isolated flagella and 2 present both in flagella and head plasma membranes) within the protein spots affected by the freezing-thawing procedure. 3 out of 4 proteins from isolated flagella were involved in the sperm bioenergetic system. Our results indicate that the ability of AFPIII to protect sea bream sperm quality can be, at least in part, ascribed to reducing changes in the sperm protein profile occurring during the freezing-thawing procedure. Our results clearly demonstrated that AFPIII addition to cryopreservation medium improved the protection against freezing respect to DMSO or DMSO plus AFPI. In addition we propose specific proteins of spermatozoa as markers related to the procedures of fish sperm cryopreservation.