Ram sperm cryopreservation disrupts metabolism of unsaturated fatty acids

Identification of key genes and variants associated with boar sperm freezability using whole genome resequencing

Cryopreservation induces various cryodamages to the structural or functional aspects of boar sperm, resulting in the deterioration of sperm quality. The extent of cryodamages varies significantly among different individual boars. In our study, 50 boars with either good sperm freezability (GSF) or poor sperm freezability (PSF) were selected from a population of 402 boars. These two groups exhibited significant differences in sperm quality, acrosome integrity, mitochondrial membrane potential, and plasma membrane integrity. Subsequent whole-genome resequencing and FST analysis of GSF and PSF boars uncovered genetic differentiation among 5632 genes. Spermatogenesis, sperm structure, and lipid composition were identified as the potential factors, and 35 genes, such as RNF8, PACRG, CADM1, SPAG16, PPP3CA and MFF, were identified as key candidate genes associated with sperm freezability. Furthermore, by using MassARRAY genotyping and a general linear model, nine variants, including seven single nucleotide polymorphisms (SNPs) and two insertion variants, were found to be significantly correlated with sperm freezability. These variants, located within the candidate genes, represent potential molecular markers for sperm freezability. Our research contributes novel insights into the genetic mechanisms underlying freezability differences in boar sperm and identifies candidate genes and key molecular markers that could be applied in boar breeding practices.

Sodium alginate and bovine serum albumin co-combined improved the cryopreservation quality of boar sperm through the PI3K-AKT pathway

Context The occurrence of apoptosis due to transient oxidative damage to spermatozoa presents a significant challenge in semen preservation. At present, the addition of protective agents is the primary method for mitigating this damage and involves the addition of protective agents. Aims This study aims to elucidate the mechanism of action of cryopreservation and to identify high-quality combinatorial cryopreservation dilutions. Methods In this study, two protective agents, bovine serum albumin (BSA) and sodium alginate (SA), were combined to evaluate the effectiveness of these novel additives in protecting porcine sperm from damage during cryopreservation. The mechanism of action of the SA and BSA combination was further elucidated at the molecular level, with key proteins being identified through proteomic analysis. Key results The findings indicated that sperm treated with 2mg/mL SA and 5mg/mL BSA exhibited optimal motility parameters, superior functional integrity and the most effective ability to alleviate oxidative stress. Combined with proteomic data, the results suggested that these additives regulate improvements in sperm quality by mediating the activity of the PI3K-AKT pathway. Conclusions This study found that the combination of SA and BSA provides an effective protective effect for frozen sperm preservation. Implications The findings offer theoretical and technical support for the use of composite additive to protect sperm from damage, which is crucial for enhancing the quality of pig semen and improving reproductive outcomes.

Proteomics and metabolomics analyses of mechanism underlying bovine sperm cryoinjury

BACKGROUND

The cryoinjury of semen during cryopreservation reduces sperm motility, constraining the application of artificial insemination (AI) in bovine reproduction. Some fertility markers, related to sperm motility before and after freezing have been identified. However, little is known about the biological mechanism through which freezing reduces sperm motility. This study investigated the selective effects of cryoinjury on high-motility sperm (HMS) and low-motility sperm (LMS) in frozen-thawed from the perspectives of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP levels. The molecular mechanism of decreased sperm motility caused by cryoinjury was explored through a joint analysis of 4D-label free quantitative proteomics and non-targeted metabolomics.

RESULTS

The results indicate that low levels of ROS and high degrees of MMP and ATP play a critical role in the survival of HMS during the freezing process. The sperm samples from the frozen-thawed HMS and LMS were analysed for proteomics and metabolomics, 2,465 proteins and 4,135 metabolites were detected in bovine sperm samples. In contrast to LMS, HMS have 106 proteins and 106 metabolites with high abundance expression, and 79 proteins and 223 metabolites with low abundance expression. Proteomics and metabolomics data exhibit that highly expressed antioxidant enzymes and metabolites in HMS can maintain sperm motility by regulating the ROS produced during freezing to prevent sperm from oxidative stress and apoptosis. Furthermore, the KEGG analysis of differential proteins and metabolites during the freezing process implies that the significant enrichment of glycolysis and cAMP in HMS can guarantee energy supply.

CONCLUSIONS

The results provided that during the process of bovine sperm freezing, highly expressed antioxidant enzymes can regulate the reactive oxygen species levels to avoid oxidative stress and the glycolysis signalling pathway ensures ATP production can sustain frozen-thawed sperm motility.

Abnormalities in mitochondrial energy metabolism induced by cryopreservation negatively affect goat sperm motility

The motility of sperm decreases following cryopreservation, which is closely associated with mitochondrial function. However, the alterations in mitochondrial metabolism after sperm freezing in goats remain unclear. This experiment aimed to investigate the impact of ultra-low temperature freezing on goat sperm's mitochondrial energy metabolism and its potential correlation with sperm motility. The results revealed that goat sperm exhibited mitochondrial vacuolization, reduced matrix density, and significantly decreased levels of high-membrane potential mitochondria and adenosine triphosphate content, accompanied by a substantial increase in reactive oxygen species levels, ultimately leading to a significant decline in sperm viability. Further investigations unveiled that energy-related differential metabolites (capric acid, creatine, and D-glucosamine-6-phosphate) and differential metabolites with antioxidant effects (saikosaponin A, probucol, and cholesterol sulfate) were significantly downregulated. In addition, the activity of key rate-limiting enzymes involved in very long-chain fatty acid biosynthesis and β-oxidation-specifically acetyl-CoA carboxylase, fatty acid synthase, and carnitine palmitoyltransferase I related to capric acid metabolism-was considerably reduced. Furthermore, supplementation of differential metabolite capric acid (500 μM) significantly enhanced the motility of frozen-thawed goat sperm. These findings indicated that the mitochondrial ultrastructure of goat sperm is damaged and energy metabolism becomes abnormal after cryopreservation, potentially affecting sperm viability. The addition of different metabolites such as capric acid to the freezing extender can alleviate the decrease in sperm motility induced by cryopreservation.

Dexamethasone and azithromycin enhance goat sperm preservation quality by regulating lipid metabolism

Phospholipase A (PLA) in goat semen aggregates with egg yolk in semen diluent, leading to sperm death. The aim of this study is to address the issue of sperm death caused by the interaction between PLA and egg yolk, and to explore the protective effect and metabolic regulation mechanism of the combination of dexamethasone (DXMS) and azithromycin (AZM) on goat sperm under low temperature conditions. At a low temperature of 4 °C, different concentrations of DXMS were added to semen diluents containing 30 μg/mL AZM to detect the quality of goat sperm. The optimal concentration of DXMS was determined to be 20 μg/mL. On the 5th day of storage, antioxidant capacity, total cholesterol (TC) levels, energy metabolism, and metabolomics analysis were performed on the sperm of the 20 μg/mL DXMS group. The results showed that there was no aggregation caused by the interaction between PLA and egg yolk in the group containing 30 μg/mL AZM at 4 °C. 20 μg/mL DXMS significantly improved sperm motility, plasma membrane integrity, acrosome integrity, glutathione peroxidase (GPX) (P < 0.05), catalase (CAT) (P < 0.01), and superoxide dismutase (SOD) activity (P < 0.01). The content of reactive oxygen species (ROS) and Fe2+ significantly decreased (P < 0.01), while the content of ATP (P < 0.01) and TC (P < 0.05) significantly increased. Through metabolomics analysis, a total of 56 differential metabolites (P < 0.05) were screened, including 5a, 6-Anhydrotetracycline, Betamethasone, and 11-Dehydrocorticosterone, mainly enriched in 8 metabolic pathways (P < 0.05), including steroid hormone biosynthesis, glycerophospholipid metabolism, and choline metabolism in cancer. Among them, 5 metabolic pathways are related to lipid metabolism. The results indicate that AZM effectively inhibits the aggregation of PLA and yolk, and the combination of AZM and DXMS enhances the preservation quality of goat sperm during low-temperature preservation by regulating lipid metabolism.

Sperm Human Biobanking: An Overview

The purpose of this article is to analyze in detail the advantages and disadvantages of sperm cryopreservation, focusing on the cellular and molecular changes that occur during these processes. The main issue is the cellular damage caused by ice crystal formation and osmotic imbalance, along with other secondary effects such as sperm motility and viability, as well as the acrosome reaction or oxidative stress. Another important aspect is the examination of how chromatin structure and DNA integrity affect sperm. Biochemical changes affecting enzyme activity and protein stability have also been analyzed. Finally, the article highlights emerging technologies aimed at reducing the damage caused by sperm cryopreservation, as well as the potential benefits of biobanks as an essential resource for addressing male infertility.

Anethole improves mitochondrial activity and quality parameters in fresh and frozen-thawed ovine semen

Anethole, an antioxidant found in plants, appears to improve the survival of spermatozoa during semen cryopreservation. This study assessed the effects of commercial trans-anethole in ram semen cryopreservation. Thirty ejaculates from six rams were diluted in media containing anethole at the following concentrations: CONT (0 μM), AN10 (10 μM), AN50 (50 μM), and AN100 (100 μM). Semen was slow-frozen, preserved in liquid nitrogen, and thawed. Anethole at 10 μM or 50 μM did not compromise any studied sperm quality parameter but increased pre-freezing functionality of membrane and mitochondrial activity. At 10 μM, anethole reduced post-thawing spermatozoa lipoperoxidation. At 50 μM, anethole sustained higher mitochondrial activity after thawing, reduced minor defects in sperm, and increased the number of sperm binding to perivitelline membrane, while keeping lipoperoxidation levels as in control. Anethole at 100 μM promoted higher pre- and post-freezing mitochondrial activity and higher number of sperm binding to perivitelline membrane, in comparison to control. Additionally, some post-thawing kinematic parameters were enhanced by anethole at 100 μM. Of note, mitochondrial activity and lipoperoxidation were higher with anethole at 100 μM in comparison to 50 μM, not differing from control. At the hypoosmotic test, the highest concentration (100 μM) tested reduced sperm osmotic resistance. The results of this study indicate that using anethole in cryopreservation media promoted mostly positive effects on the fresh and post-thawed ram semen, and the advantages vary according to its concentration.

A review on the functional roles of trehalose during cryopreservation of small ruminant semen

Sperm cryopreservation is an approach to preserve sperm cells in liquid nitrogen or other cryogenic media for future use in assisted reproductive technologies, such as in vitro fertilization or artificial insemination. Sperm cryopreservation has been extensively used in the dairy industry and has attained excellent results after artificial insemination. However, for small ruminants the application of sperm cryopreservation is limited, due to the poor quality of frozen semen and special characteristics of the reproductive female tract. In order to improve post-thaw semen quality various cryoprotectants are used. Currently, many types of cryoprotectants, such as permeable organic solvents, sugars, antioxidants, and natural or synthetic ice blockers, have been tested on small ruminants' sperm cryopreservation. Among them, trehalose; has shown potential acting as an excellent cryoprotectant for semen freezing. While, the exact roles and action mechanisms of trehalose during cryopreservation remain unclear. In this review, we systematically summarized the present usage status, potential action mechanisms, and future application prospects of trehalose in small-ruminant sperm cryopreservation.

Sperm Metabolism

Bioenergetics plays a crucial role in sperm functions, including motility, capacitation-related protein modifications, oocyte recognition and interaction, all of which are essential for fertilization. Sperm metabolism is recognized as flexible, responding to environmental cues and energetic demands during ejaculation, the journey along the female tract, and until fertilization. Recent studies suggest that sperm metabolic functions are relevant beyond fertilization and may influence zygote and embryo development, impacting paternal-derived effects on offspring development and health. In recent years, sperm metabolic functions and homeostasis have gained increasing interest in male reproduction research. Given the crucial implications of sperm metabolism on fertility-related processes, this field is of interest not only in human male fertility but also in livestock research, semen conservation, and assisted reproductive techniques. Newly developed assessment tools are allowing a better understanding of sperm metabolism under different conditions and identifying species-specific peculiarities. This review aims to discuss the current knowledge of mammalian sperm metabolism, focusing on species-specific features, changes during the sperm journey, and potential contributions to translational research and reproductive biotechnologies. Furthermore, we propose future perspectives on sperm bioenergetics research.

Revisiting the Injury Mechanism of Goat Sperm Caused by the Cryopreservation Process from a Perspective of Sperm Metabolite Profiles

Semen cryopreservation results in the differential remodeling of the molecules presented in sperm, and these alterations related to reductions in sperm quality and its physiological function have not been fully understood. Given this, this study aimed to investigate the cryoinjury mechanism of goat sperm by analyzing changes of the metabolic characteristics in sperm during the cryopreservation process. The ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) technique was performed to explore metabolite profiles of fresh sperm (C group), equilibrated sperm (E group), and frozen-thawed sperm (F group). In total, 2570 metabolites in positive mode and 2306 metabolites in negative mode were identified, respectively. After comparative analyses among these three groups, 374 differentially abundant metabolites (DAMs) in C vs. E, 291 DAMs in C vs. F, and 189 DAMs in E vs. F were obtained in the positive mode; concurrently, 530 DAMs in C vs. E, 405 DAMs in C vs. F, and 193 DAMs in E vs. F were obtained in the negative mode, respectively. The DAMs were significantly enriched in various metabolic pathways, including 31 pathways in C vs. E, 25 pathways in C vs. F, and 28 pathways in E vs. F, respectively. Among them, 65 DAMs and 25 significantly enriched pathways across the three comparisons were discovered, which may be tightly associated with sperm characteristics and function. Particularly, the functional terms such as TCA cycle, biosynthesis of unsaturated fatty acids, sphingolipid metabolism, glycine, serine and threonine metabolism, alpha-linolenic acid metabolism, and pyruvate metabolism, as well as associated pivotal metabolites like ceramide, betaine, choline, fumaric acid, L-malic acid and L-lactic acid, were focused on. In conclusion, our research characterizes the composition of metabolites in goat sperm and their alterations induced by the cryopreservation process, offering a critical foundation for further exploring the molecular mechanisms of metabolism influencing the quality and freezing tolerance of goat sperm. Additionally, the impacts of equilibration at low temperature on sperm quality may need more attentions as compared to the freezing and thawing process.

Quantitative phosphoproteomics explain cryopreservation-induced reductions in ram sperm motility

Sperm cryopreservation decreases motility, probably due to changes in protein phosphorylation. Our objective was to use quantitative phosphoproteomics for systematic comparative analyses of fresh versus frozen-thawed sperm to identify factors causing cryo-injury. Ejaculates were collected (artificial vagina) from six Dorper rams, pooled, extended, and frozen over liquid nitrogen. Overall, 915, 3382, and 6875 phosphorylated proteins, phosphorylated peptides, and phosphorylation sites, respectively, were identified. At least two modified sites were present in 57.94% of the 6875 phosphosites identified, of which AKAP4 protein contained up to 331 modified sites. There were 732 phosphorylated peptides significantly up-regulated and 909 significantly down-regulated in frozen-thawed versus fresh sperm. Moreover, the conserved motif [RxxS] was significantly down-regulated in frozen-thawed sperm. Phosphorylation of sperm-specific proteins, e.g., AKAP3/4, CABYR, FSIP2, GSK3A/B, GPI, and ODF1/2 make them potential biomarkers to assess the quality of frozen-thawed ram sperm. Furthermore, these differentially phosphorylated proteins and modification sites were implicated in cryopreservation-induced changes in sperm energy production, fiber sheath composition, and various biological processes. We concluded that abnormal protein phosphorylation modifications are key regulators of reduced sperm motility. These novel findings implicated specific protein phosphorylation modifications in sperm cryo-injury. SIGNIFICANCE: This study used phosphorylated TMT quantitative proteomics to explore regulation of epigenetic modifications in frozen-thawed ram sperm. This experiment demonstrated that ram sperm freezing affects phosphorylation site modifications of proteins, especially those related to functions such as sperm motility and energy production. Furthermore, it is important to link functions of phosphorylated proteins with changes in sperm quality after freezing and thawing, and to clarify intrinsic reasons for sperm quality changes, which is of great importance for elucidating mechanisms of sperm freezing damage. Based on these protein markers and combined with cryoprotectant design theory, it provides a theoretical basis and data reference to study sperm cryoprotectants.

Improving chilled and frozen buck sperm characteristics by adding melatonin and L-carnitine to the preservation medium

This study evaluated the effects of melatonin (MLT) and L-carnitine supplementation on sperm quality and antioxidant capacity during chilled and cryopreservation. Twenty-four ejaculates were collected from six Damascus bucks, 4 ejaculates each, from mid-September to mid-October 2022. The pooled semen from each collecting session was divided into 5 equal aliquots after being diluted (1:10) with Tris-citric acid egg yolk extender. The first aliquot served as a control (treatment-free). MLT was added to the second and third aliquots at low and high doses (LD: 4 and HD: 8 μL/mL) (v/v), respectively, while L-carnitine (LC) was added to the fourth and fifth aliquots at the same aforementioned doses. The aliquots were stored at 4°C for 48 h to assess sperm physical and morphological characteristics, alongside lipids peroxidase (LP) production and glutathione peroxidase (GPX) activity. The optimum doses of MLT and LC that showed potential for maintaining sperm characteristics throughout the chilled storage period were further investigated for protecting the spermatozoa after exposure to cryopreservation stress compared to the control. The results showed higher sperm motility (%) in the MLT-HD group, higher (p ≤ .05) sperm viability (%) in the MLT-LD, and both aliquots of LC at T24 hours of chilled preservation. Normal sperm (%) was higher (p ≤ .05) in both LC-LD and MLT-LD groups than other groups, while sperm acrosome integrity (%) was higher (p ≤ .05) in the LC-LD group. Morphological abnormalities (%) were improved (p ≤ .05) in all treated aliquots compared with control. The mean value of GPX activity was higher (p ≤ .05) in both MLT groups, while the concentration of LP increased (p ≤ .05) in the LC-HD or control groups. Furthermore, supplementing buck sperm medium with 4 μL/mL of MLT or LC improved (p < .05) the sperm characteristics and decreased (p < .05) DNA fragmentation index after thawing.

Resveratrol Improves the Frozen-Thawed Ram Sperm Quality

Cryopreservation generates a substantial quantity of ROS in semen, leading to a decline in sperm quality and fertilization capacity. The objective of this study was to investigate the effects of resveratrol and its optimal concentration on ram sperm quality after cryopreservation. Ram semen was diluted with a freezing medium containing different concentrations of resveratrol (0, 25, 50, 75, and 100 μM). After thawing, various sperm parameters such as total motility, progressive motility, acrosome integrity, plasma membrane integrity, mitochondrial membrane potential, glutathione (GSH) content, glutathione synthase (GPx) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, lipid peroxidation (LPO) content, malondialdehyde (MDA) content, ROS level, SIRT1 level, DNA oxidative damage, and AMPK phosphorylation level were assessed. In addition, post-thaw sperm apoptosis was evaluated. Comparatively, the addition of resveratrol up to 75 μM significantly improved the sperm motility and sperm parameters of cryopreserved ram sperm. Specifically, 50 μM resveratrol demonstrated a notable enhancement in acrosome and plasma membrane integrity, antioxidant capacity, mitochondrial membrane potential, adenosine triphosphate (ATP) content, SIRT1 level, and AMPK phosphorylation levels compared to the control group (p < 0.05). It also significantly (p < 0.05) reduced the oxidative damage to sperm DNA. However, detrimental effects of resveratrol were observed at a concentration of 100 μM resveratrol. In conclusion, the addition of 50 μM resveratrol to the cryopreservation solution is optimal for enhancing the quality of cryopreserved ram sperm.

Evaluation of the effect of melatonin implantation in rams and eCG dose in ewes synchronized by a CIDR-eCG protocol on reproductive performance of Lacaune sheep breed during non-breeding season

Sustainable production of milk is favorable in dairy sheep industry, which necessitates year-round reproduction of rams and ewes even during non-breeding season. Hence, protocols facilitating reproduction of rams and ewes during non-breeding season are of importance for this purpose. Therefore, the present study was conducted to investigate the effect of melatonin implantation in rams and administration of 400 IU eCG (E400) versus 300 IU eCG (E300) in ewes on reproductive performance of Lacaune sheep breed during non-breeding season. Rams were allocated to two groups including untreated (control, CON; n = 36) and melatonin-treated (MEL; n = 37). A subset of rams from CON (n = 7) and MEL (n = 7) groups were used for assessment of scrotal circumference, kinematic and functional characteristics of sperm, total antioxidant capacity (TAC) of semen and circulating testosterone on Days 0 (the beginning of study) and 60 (60 days after melatonin implantation). Further, the study had a 2 × 2 factorial design with four experimental groups including 1) ewes treated with E300 and introduced to CON rams (E300CON; n = 17 rams and 172 ewes), 2) ewes treated with E300 and introduced to MEL rams (E300MEL; n = 18 rams and 177 ewes), 3) ewes treated with E400 and introduced to CON rams (E400CON; n = 19 rams and 192 ewes), and ewes treated with E400 and introduced to MEL rams (E400MEL; n = 19 rams and 190 ewes). Melatonin implantation improved scrotal circumference, concentration, progressive motility, velocity, mitochondrial membrane potential and viability of sperm, TAC of semen, concentration of testosterone and fertility of rams (P < 0.05). Besides, E400 compared with E300 enhanced synchronization of estrus and fertility in ewes (P < 0.05). In conclusion, melatonin implantation promoted reproductive performance in Lacaune rams, and increase in dose of eCG improved reproductive performance in Lacaune ewes.