The effect of cysteine and glutamine on human sperm functional parameters during vitrification

Evaluation of microRNA expression profiles in human sperm frozen using permeable cryoprotectant-free droplet vitrification and conventional methods

For sperm cryopreservation, the conventional method, which requires glycerol, has been used for a long time. In addition, the permeable cryoprotectant-free vitrification method has been continuously studied. Although the differences of cryopreservation effects between the two methods have being studied, differences in microRNA (miRNA) profiles between them remain unclear. In this study, we investigated the differences in miRNA expression profiles among conventional freezing sperm, droplet vitrification freezing sperm and fresh human sperm. We also analyzed the differences between these methods in terms of differentially expressed miRNAs (DEmiRs) related to early embryonic development and paternal epigenetics. Our results showed no significant differences between the cryopreservation methods in terms of sperm motility ratio, plasma membrane integrity, DNA integrity, mitochondrial membrane potential, acrosome integrity, and ultrastructural damage. However, sperm miRNA-sequencing showed differences between the two methods in terms of the numbers of DEmiRs (28 and 19 with vitrification using a nonpermeable cryoprotectant and the conventional method, respectively) in postthaw and fresh sperm specimens. DEmiRs related to early embryonic development and paternal epigenetics mainly included common DEmiRs between the groups. Our results showed that the differences between conventional freezing and droplet vitrification were minimal in terms of miRNA expression related to embryonic development and epigenetics. Changes in sperm miRNA expression due to freezing are not always detrimental to embryonic development. This study compared differences in miRNA expression profiles before and after cryopreservation between cryopreservation by conventional and vitrification methods. It offers a new perspective to evaluate various methods of sperm cryopreservation.

Protective effects of l-cysteine and N-acetyl-l-cysteine on boar sperm quality during hypothermic liquid storage with bovine serum albumin as a protectant

Hypothermic liquid storage at 4-5 °C has emerged as a novel approach for preserving boar semen, offering innovative possibilities for semen preservation. However, this method also presents challenges, including cold shock and excessive reactive oxygen species (ROS) production. Therefore, reducing oxidative damage induced by low temperatures becomes essential while supplementing appropriate protectants. In this study, we investigated the efficacy of Bovine Serum Albumin (BSA) compared to Polyvinylpyrrolidone (PVP) and Skim Milk Powder (SMP) in maintaining boar sperm motility and progressive motility using computer-assisted sperm analysis (CASA). Among the tested concentrations, 4 g/L of BSA exhibited the best protective effect. Subsequently, we supplemented different concentrations of l-cysteine (LC) and N-acetyl-l-cysteine (NAC) as additives in the presence of BSA as a protectant. Our results demonstrated that 1 mmol/L of LC and 0.5 mmol/L of NAC exhibited superior protection of sperm quality compared to other concentrations. Furthermore, the 1 mmol/L LC and 0.5 mmol/L NAC groups showed significantly improved plasma membrane integrity and acrosome integrity compared to the control group. These groups also exhibited enhanced antioxidant capacity, evidenced by increased mitochondrial membrane potential (MMP), ATP production, total superoxide dismutase (T-SOD) activity, total antioxidant capacity (T-AOC), glutathione (GSH), glutathione peroxidase (GSH-PX), and GPX-4 levels. Additionally, they demonstrated decreased reactive oxygen species (ROS) and malondialdehyde (MDA) levels, as well as reduced oxidized glutathione (GSSG) and glutathione reductase (GR) levels. Furthermore, LC and NAC treatment enhanced AMP-activated protein kinase (AMPK) phosphorylation. However, inhibiting AMPK using compound C did not inhibit the protective effects of LC and NAC on low-temperature preserved boar sperm. These findings suggest that 4 g/L BSA can serve as an effective protectant for hypothermic liquid storage of boar semen. Additionally, LC and NAC supplementation reduces oxidative damage by enhancing antioxidant capacity rather than through AMPK-mediated ATP supplementation. These results contribute to advancing the application of LC and NAC in hypothermic liquid storage of boar semen.

The effect of the mitochondria-targeted antioxidant Mito-tempo during sperm ultra-rapid freezing

During the freeze-thaw process, human spermatozoa are susceptible to oxidative stress, which may cause cryodamage and reduce sperm quality. As a novel mitochondria-targeted antioxidant, Mito-tempo has been used for sperm cryopreservation. However, it is currently unknown what role it will play in the process of sperm ultra-rapid freezing. The purpose of this study was to investigate whether Mito-tempo can improve sperm quality during ultra-rapid freezing. In this study, samples with the addition of Mito-tempo (0, 5, 10, 20, and 40 μM) to sperm freezing medium were selected to evaluate the changes in sperm quality, antioxidant capacity and ultrastructure after ultra-rapid freezing. After ultra-rapid freezing, the quality and antioxidant function of the spermatozoa were significantly reduced and the spermatozoa ultrastructure was destroyed. The addition of 10 μM Mito-tempo significantly increased post thaw sperm motility, viability, plasma membrane integrity and mitochondrial membrane potential (P < 0.05). Moreover, the DNA fragmentation index (DFI), ROS levels and MDA content were reduced, and the antioxidant enzyme (CAT and SOD) activities were enhanced in the 10 μM Mito-tempo group (P < 0.05). Moreover, Mito-tempo protected sperm ultrastructure from damage. In conclusion, Mito-tempo improved the quality and antioxidant function of sperm after ultra-rapid freezing while reducing freezing-induced ultrastructural damage.

Evaluation of the effect of mitoquinone on functional parameters, DNA structure, and genes expression related to the apoptotic and antioxidants of human sperm after freezing-thawing

OBJECTIVE

Sperm freezing is considered as an effective way in assisted reproductive technology (ART) programs, it has detrimental effects on sperm function, due to the production of reactive oxygen species (ROS). This study aimed to investigate the potential of Mitoquinone (MitoQ) in inhibiting the production of mitochondrial ROS during sperm freezing.

METHODS

A total of 20 human normozoosperm samples were collected for this study. The samples were divided into four groups, each containing different concentrations of MitoQ (0, 0.2, 2, and 20 nM), and then subjected to the freezing process. After thawing, the sperm suspensions were evaluated for parameters including motility, morphology, acrosome integrity, adenosine triphosphate (ATP) level, intracellular ROS, viability, chromatin packaging, DNA denaturation, DNA fragmentation, as well as the expression of antioxidants (GPX, SOD) and apoptotic (Bax, Bcl2) genes.

RESULTS

The results showed that total and progressive mobility of sperms significantly increased in the 2 nM group, while significantly decreased in the 20 nM group (p ≤ 0.05). Sperm morphology did not significantly improve across all the tested concentrations (p ≥ 0.05). Intracellular ROS levels showed a significant decrease and increase in the concentrations of 2 and 20 nM, respectively (p ≤ 0.05). Furthermore, a significant increase was observed in viability, ATP, acrosome integrity, chromatin packaging, and non-denatured and non-fragmented DNA after treatment with 2 nM of MitoQ, compared with the control group (p ≤ 0.05). Regarding gene expressions, the relative expressions of oxidative stress genes were increased in the 2 nM group and decreased in the 20 nM group (p ≤ 0.05), while no significant difference was observed in the expressions of apoptotic genes compared with the control group (p ≥ 0.05). All the comparisons were made with respect to the control group.

CONCLUSION

Adding the optimal concentration of MitoQ (2 nM) to the sperm freezing medium not only improves sperm functional parameters and reduces DNA damages, but also stimulates the expression of antioxidant genes, leading to even greater benefits for sperm cryopreservation.

Targeted Amino Acids Profiling of Human Seminal Plasma from Teratozoospermia Patients Using LC-MS/MS

Identifying the metabolome of human seminal plasma (HSP) is a new research area to screen putative biomarkers of infertility. This case-control study was performed on HSP specimens of 15 infertile patients with teratozoospermia (defined as normal sperm morphology < 4%) and 12 confirmed fertile normozoospermic men as the control group to investigate the seminal metabolic signature and whether there are differences in the metabolome between two groups. HSPs were subjected to LC-MS-MS analysis. MetaboAnalyst5.0 software was utilized for statistical analysis. Different univariate and multivariate analyses were used, including T-tests, fold change analysis, random forest (RF), and metabolite set enrichment analysis (MSEA). Teratozoospermic samples contained seventeen significantly different amino acids. Upregulated metabolites include glutamine, asparagine, and glycylproline, whereas downregulated metabolites include cysteine, γ-aminobutyric acid, histidine, hydroxylysine, hydroxyproline, glycine, proline, methionine, ornithine, tryptophan, aspartic acid, argininosuccinic acid, α-aminoadipic acid, and β-aminoisobutyric acid. RF algorithm defined a set of 15 metabolites that constitute the significant features of teratozoospermia. In particular, increased glutamine, asparagine, and decreased cysteine, tryptophan, glycine, and valine were strong predictors of teratozoospemia. The most affected metabolic pathways in teratozoospermic men are the aminoacyl-tRNA, arginine, valine-leucine, and isoleucine biosynthesis. Altered metabolites detected in teratozoospermia were responsible for various roles in sperm functions that classified into four subgroups as follows: related metabolites to antioxidant function, energy production, sperm function, and spermatogenesis. The altered amino acid metabolome identified in this study may be related to the etiology of teratozoospermia, and may provide novel insight into potential biomarkers of male infertility for therapeutic targets.

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

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

Human sperm parameter improvement associated with Ceratonia siliqua extract as a cryopreservation supplement after vitrification

OBJECTIVE

Given the destructive effects of oxidative stress on sperm structure, this study was conducted to investigate the antioxidant effects of different concentrations of Ceratonia siliqua plant extract on human sperm parameters after the freezing-thawing process.

METHODS

A total of 20 normozoospermic samples were frozen. Each sample was divided into two control groups (fresh and cryopreservation) and three cryopreservation experimental groups (containing C. siliqua extract at concentrations of 20, 30, and 40 μg/mL in the freezing extender). Motility, intracellular levels of reactive oxygen species (ROS), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), viability, and acrosome reaction parameters were evaluated.

RESULTS

Statistical analysis showed that the highest motility, viability, and PMI were associated with the 20 μg/mL concentration of C. siliqua extract. At all concentrations, intracellular ROS levels were significantly lower and the levels of MMP and the acrosome reaction were significantly higher than in the cryopreservation control group (p≤0.05).

CONCLUSION

C. siliqua extract supplements at concentrations of 20, 30, and 40 μg/mL improved sperm motility, viability, PMI, MMP, intracellular ROS, and the acrosome reaction.

The effects of purslane (Portulaca oleracea) and fennel (Foeniculum vulgare Mill) hydroalcoholic extracts on the functional parameters of human spermatozoa after vitrification

OBJECTIVE

Reactive oxygen species (ROS) are produced during cryopreservation of human sperm and impair sperm function. Antioxidant compounds, such as fennel and purslane, reduce the damaging effects of ROS. This study aimed to evaluate motility parameters, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), intracellular ROS, and DNA damage to determine the optimum concentrations of hydroalcoholic extracts of fennel and purslane for human spermatozoa cryopreservation.

METHODS

Twenty human sperm samples were used and divided into seven equal groups consisting of fennel hydroalcoholic extract (5, 10, and 15 mg/L), purslane hydroalcoholic extract (25, 50, and 100 mg/L), and no additive.

RESULTS

Supplementation of 25 mg/L and 50 mg/L purslane extract and 10 mg/L fennel extract in cryopreservation extender significantly increased the motility and PMI of sperm with a significant reduction in intracellular ROS compared to control groups (p<0.05). A 50 mg/L concentration of purslane extract elevated progressive motility and MMP compared to the control group (p<0.05). No significant differences were seen for motion patterns and DNA damage of frozen-thawed human sperm in extender containing these extracts.

CONCLUSION

The results showed that supplementation of 50 mg/L purslane extract and 10 mg/L fennel extract in semen cryopreservation extender has the potential to decrease intracellular ROS and subsequently elevate the motility and PMI of human sperm.

A Metabolomic Profile of Seminal Fluid in Extremely Severe Oligozoopermia Suggesting an Epididymal Involvement

Male infertility has increased in the last decade. Pathophysiologic mechanisms behind extreme oligospermia (EO) are not yet fully understood. In new “omics” approaches, metabolomic can offer new information and help elucidate these mechanisms. We performed a metabolomics study of the seminal fluid (SF) in order to understand the mechanisms implicated in EO. We realized a targeted quantitative analysis using high performance liquid chromatography and mass spectrometry to compare the SF metabolomic profile of 19 men with EO with that of 22 men with a history of vasectomy (V) and 20 men with normal semen parameters (C). A total of 114 metabolites were identified. We obtained a multivariate OPLS-DA model discriminating the three groups. Signatures show significantly higher levels of amino acids and polyamines in C group. The sum of polyunsaturated fatty acids and free carnitine progressively decrease between the three groups (C > EO > V) and sphingomyelins are significantly lower in V group. Our signature characterizing EO includes metabolites already linked to infertility in previous studies. The similarities between the signatures of the EO and V groups are clear evidence of epididymal dysfunction in the case of testicular damage. This study shows the complexity of the metabolomic dysfunction occurring in the SF of EO men and underlines the importance of metabolomics in understanding male infertility.

Advantages of vitrification preservation in assisted reproduction and potential influences on imprinted genes

Cryopreservation has important application in assisted reproductive technology (ART). The vitrification technique has been widely used in the cryopreservation of oocytes and embryos, as a large number of clinical results and experimental studies have shown that vitrification can achieve a higher cell survival rate and preimplantation development rate and better pregnancy outcomes. Ovarian tissue vitrification is an alternative method to slow freezing that causes comparatively less damage to the original follicular DNA. At present, sperm preservation mainly adopts slow freezing or rapid freezing (LN2 vapor method), although the vitrification method can achieve higher sperm motility after warming. However, due to the use of high-concentration cryoprotectants and ultra-rapid cooling, vitrification may cause strong stress to gametes, embryos and tissue cells, resulting in potentially adverse effects. Imprinted genes are regulated by epigenetic modifications, including DNA methylation, and show single allele expression. Their accurate regulation and correct expression are very important for the placenta, fetal development and offspring health. Considering that genome imprinting is very sensitive to changes in the external environment, we comprehensively summarized the effect of cryopreservation—especially the vitrification method in ART—on imprinted genes. Animal studies have found that the vitrification of oocytes and embryos can have a significant impact on some imprinted genes and DNA methylation, but the few studies in humans have reported almost no influence, which need to be further explored. This review provides useful information for the safety assessment and further optimization of the current cryopreservation techniques in ART.

Ultra-Rapid Freezing Preserves Morphofunctional Integrity and Fertilizing Ability of Epididymal Cat Spermatozoa

Vitrification and ultra-rapid freezing, which are more commonly used for oocytes and embryos, have recently been applied to spermatozoa in an attempt to make semen cryopreservation in field conditions easier compared to conventional freezing. It is well-known that in case of unexpected death of rare and wild animals, preserving epididymal spermatozoa from isolated testicles represents a great chance of salvaging male germplasm for future use in assisted reproductive technologies. The aim of this study was to evaluate the morphofunctional integrity of cat epididymal spermatozoa ultra-rapid frozen in pellets or straws with two different extenders [E1 (Tris buffer with 20% egg yolk and 0.25 M sucrose) or E2 (Ham's F10 with 1% bovine serum albumin and 0.4 M sucrose)] and to test whether spermatozoa preserved by the best combination were able to fertilize oocytes and produce embryos in vitro by intracytoplasmic sperm injection (ICSI) of in vitro matured cat oocytes. The results showed that E1 and E2 in straw or pellet were comparable (at warming, about 30% normal morphology, 45% intact membranes, and 20% intact acrosomes), except for post-warming motility that was better maintained along time by E1 pellet (21.7 ± 7.4% at warming and 3.6 ± 2.9% after 6 h). Such spermatozoa could fertilize conspecific oocytes and support embryonic development (cleavage 35.5%) as well as frozen control spermatozoa (cleavage 54.29%, p = 0.22). In conclusion, cat epididymal spermatozoa better maintained their morphofunctional features after ultra-rapid freezing with E1 and could successfully produce embryos in vitro after ICSI. This underscores their usefulness as cryobanked material for fertility and biodiversity preservation purposes.

Melatonin and selenium supplementation in extenders improves the post-thaw quality parameters of rat sperm

Objective

The aim of this study was to determine the effects of melatonin and selenium in freezing extenders on frozen-thawed rat sperm.

Methods

Semen samples were collected from 20 adult male Wistar albino rats. Following dilution, the samples were divided into six groups: four cryopreserved groups with 1 mM and 0.5 mM melatonin and selenium supplements, and two fresh and cryopreserved control groups. The rapid freezing technique was used to freeze the samples. Flow cytometry was used to assess plasma membrane integrity, mitochondrial membrane potential, and DNA damage, while computer-assisted sperm analysis was used to assess motility.

Results

Total motility was higher in the 1 mM melatonin supplementation group than in the cryopreserved control group (mean±standard error of the mean, 69.89±3.05 vs. 59.21±1.31; p≤0.05). The group with 1 mM selenium had the highest plasma membrane integrity (42.35%±1.01%). The cryopreserved group with 0.5 mM selenium had the highest mitochondrial membrane potential, whereas the cryopreserved control group had the lowest (45.92%±4.53% and 39.45%±3.52%, respectively).

Conclusion

Cryopreservation of rat semen supplemented with 1 mM melatonin increased sperm motility after freeze-thawing, while supplementation with 0.5 mM selenium increased mitochondrial activity.

The relationship between reactive oxygen species, DNA fragmentation, and sperm parameters in human sperm using simplified sucrose vitrification with or without triple antioxidant supplementation

Objective

This study examined whether the addition of triple antioxidants (3A)—10 µM acetyl-L-carnitine, 10 µM N-acetyl-L-cysteine, and 5 µM α-lipoic acid—in freezing-thawing medium during human sperm cryopreservation using the sucrose vitrification (SuV) and liquid nitrogen vapor (Vapor) techniques could improve post-thaw survival of spermatozoa.

Methods

We analyzed 30 samples from healthy human sperm donors. Each sample was allocated into one of five groups: fresh control, SuV, SuV+3A, Vapor, and Vapor+3A. The sperm motility, morphology, viability, intracellular and extracellular reactive oxygen species (ROS) levels, and sperm DNA fragmentation (SDF) were evaluated.

Results

The cryopreserved spermatozoa had significantly reduced percentages of motility (p<0.05) and viability (p<0.05). Antioxidant supplementation non-significantly improved these parameters (p>0.05). No significant differences were found in sperm morphology between the fresh and frozen-thawed groups (p>0.05). After freezing, the extracellular ROS levels in the frozen-thawed groups were significantly higher (p<0.05) than in the fresh group. However, we did not find any differences in intracellular ROS parameters among these groups (p>0.05). The SDF was higher in the SuV and Vapor groups than in the fresh group, but without statistical significance (p=0.075 and p=0.077, respectively).

Conclusion

Cryopreservation had detrimental effects on sperm motility, viability, and extracellular ROS levels, without changing the morphology or intracellular ROS levels. Antioxidant supplementation was slightly effective in preventing SDF in frozen-thawed spermatozoa.

Effect of aqueous Nigella sativa extract on the functional parameters of post-thaw human spermatozoa during vitrification

Objective

Sperm vitrification leads to the production of reactive oxygen species (ROS) that can damage the functional parameters of sperm. The present study aimed to investigate the antioxidant effect of Nigella sativa extract on motility, plasma membrane function, mitochondrial membrane potential (MMP), DNA damage, and intracellular ROS production.

Methods

A total of 20 sperm samples were used. Samples were divided into six experimental groups, including groups with aqueous extract from N. sativa seeds at concentrations of 1% to 6%, a cryopreserved control group, and a fresh control group.

Results

Statistical analysis showed significantly higher total sperm motility at concentrations of 3% to 6% than in the vitrified semen control group. Additionally, progressive motility and all motion characteristics at all concentrations were significantly higher than in the vitrified semen control group. The presence of N. sativa seed extract also improved the quality of the sperm parameters assayed in all experimental groups (1%–6%; intracellular ROS production, DNA damage, MMP, and sperm membrane function) compared to the control group.

Conclusion

Higher concentrations of N. sativa led to improvements in all sperm parameters and sperm quality. These findings indicate that N. sativa seed extract is effective for improving the quality of sperm after vitrification.

The antioxidant roles of L-carnitine and N-acetyl cysteine against oxidative stress on human sperm functional parameters during vitrification

Objective

Amino acids can protect sperm structure in cryopreservation due to their antioxidant properties. Therefore, the present study aimed to investigate the protective effect of L-carnitine (LC) and N-acetyl cysteine (NAC) on motility parameters, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA damage, and human sperm intracellular reactive oxygen species (ROS) during vitrification.

Methods

Twenty normal human sperm samples were examined. Each sample was divided into six equal groups: LC (1 and 10 mM), NAC (5 and 10 mM), and cryopreserved and fresh control groups.

Results

The groups treated with LC and NAC showed favorable findings in terms of motility parameters, DNA damage, and MMP. Significantly higher levels of intracellular ROS were observed in all cryopreserved groups than in the fresh group (p≤0.05). The presence of LC and NAC at both concentrations caused an increase in PMI, MMP, and progressive motility parameters, as well as a significant reduction in intracellular ROS compared to the control group (p≤0.05). The concentrations of the amino acids did not show any significant effect.

Conclusion

LC and NAC are promising as potential additives in sperm cryopreservation.