Use of Glutamine and Low Density Lipoproteins Isolated from Egg Yolk to Improve Buck Semen Freezing

Evaluation of Chicken Egg Yolk Plasma and Low-Density Lipoprotein Alone or Enriched with Ewe or Cow Skim Milk in Tris-Citric Acid-Based Diluent for Cryostorage of Ram Semen

The main purpose of the current study was to find suitable and optimum levels of protectants among chicken egg yolk plasma (CEYP) and low-density lipoproteins (LDLs), alone or supplemented with ewe or cow skim milk, for cryopreservation of ram semen. In Experiments 1 and 2, the CEYP (28%) freezing extender was enriched with ewe or cow milk (2.5%, 5%, 10%, or 20%; v/v), respectively. In Experiments 3 and 4, the semen extender was prepared by varying the amounts of fresh or lyophilized LDL (lyo-LDL), respectively. Finally, ewe or cow skim milk was added to the freshly extracted LDL extender and the quality of frozen-thawed semen was examined (Experiments 5 and 6). Kinematics of spermatozoa (assessed using a computer-assisted sperm analysis system), viability, functionality of the plasma membrane, and levels of malondialdehyde (MDA) and total antioxidant capacity (TAC) were evaluated. Results revealed that addition of ewe or cow skim milk (5%, 10%, or 20%; v/v) to the CEYP diluent enhanced kinematics, viability, and membrane integrity of spermatozoa compared with the control (p < 0.05). Moreover, fresh LDL diluent was more effective than lyo-LDL in the cryosurvival of ram spermatozoa. In addition, enrichment of fresh LDL diluent with ewe or cow skim milk improved different variables of spermatozoa compared with the control (p < 0.05). Levels of MDA and TAC were not affected by adding ewe or cow milk to the diluents (p > 0.05). In conclusion, enrichment of fresh LDL extenders with ewe or cow milk also is proposed as an approach to preserve ram semen quality against cold shock and cryodamage injuries.

Metabolomic analysis of seminal plasma to identify goat semen freezability markers

Factors affecting sperm freezability in goat seminal plasma were investigated. Based on the total motility of thawed sperm, goats were divided into a high-freezability (HF) group with &gt;60% total motility (n = 8) and a low-freezability (LF) group with &lt;45% total motility (n = 8). Sperm and seminal plasma from the HF and LF groups were separated, HF seminal plasma was mixed with LF spermatozoa, LF seminal plasma was mixed with HF sperm, and the products were subjected to a freeze-thaw procedure. Semen from individual goats exhibited differences in freezability. HF semen had higher sperm motility parameters and plasma membrane and acrosome integrity after thawing; this difference could be related to the composition of seminal plasma. Seminal plasma from the HF and LF groups was evaluated using metabolomic analysis, and multivariate statistical analysis revealed a clear separation of metabolic patterns in the seminal plasma of goats with different freezability classifications. Forty-one differential metabolites were identified using the following screening conditions: variable importance in the projection &gt; 1 and 0.05 &lt; P-value &lt; 0.1. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed significant enrichment of central carbon metabolism in cancer, protein digestion and absorption, aminoacyl-tRNA, and other pathways and significant differences in the abundance of seven differential metabolites, including L-glutamine, L-aspartate, L-arginine, phenylpyruvate, benzoic acid, ketoisocaproic acid, and choline between seminal plasma from the HF and LF groups (P-value &lt; 0.05). These significantly differentially-expressed metabolites may be potential biomarkers for sperm freezability. L-glutamine, L-aspartate, and L-arginine may directly affect sperm freezability. Benzoic acid, ketoisocaproic acid, and choline may regulate sperm freezability by participating in anabolic processes involving phenylalanine, leucine, and phosphatidylcholine in sperm.

Evaluation of pentoxifylline and Basal Medium Eagle supplemented to diluent on cryopreserved goat spermatozoa

This study investigated the effect of pentoxifylline (PTX) and Basal Medium Eagle (BME) on frozen-thawed goat spermatozoa. Immediately after initial examination of ejaculated semen, samples were pooled and reexamined for quality. Then, samples were divided into eight equal aliquots and diluted with a basic tris-extender containing PTX (3, 6, 9 mM) and BME (5 mM) to reach a final concentration of 25 × 10⁹ and frozen. After 24 hr, the samples were individually thawed at 37°C for 30 s and evaluated for different characteristics. Obtained post-thaw results from Computer-Assisted Sperm Analysis indicate using of 3 and 6 mM PTX led significantly to an improvement in total motility, progressive motility and velocity characteristics of spermatozoa, except the beat/cross frequency (BCF) which indicated statistically no differences (p > .05) among control and treatments. Diluents prepared with BME (5 mM) and PTX alone (3 and 6 mM) improved significantly the membrane integrity-functionality, acrosome integrity and also hyaluronidase activity. Regarding recovery rate, the results showed significantly (p < .05) higher values for diluents containing 3 and 6 mM PTX compared to other groups. Malondialdehyde concentration exhibited also a significant difference (p < .05) in diluents supplemented with 5 mM BME, 3, 6 and 9 mM PTX, and mixture of 3 mM PTX and 5 mM BME which illustrate a similarity for active mitochondria, apoptotic-like and dead spermatozoa. Finally, the ratio of sperm chromatin dispersion stained spermatozoa presented significant differences (p < .05) among treatments in which the diluents added PTX alone demonstrated significantly lower values than control and extenders containing the mixtures of BME and PTX. In conclusion, the observation in this study indicates using of 3 and 6 mM PTX and BME alone may improve significantly (p < .05) the quality of cryopreserved goat spermatozoa.

Amino Acids of Seminal Plasma Associated With Freezability of Bull Sperm

Sperm cryopreservation is an important technique for fertility management, but post-thaw viability of sperm differs among breeding bulls. With metabolites being the end products of various metabolic pathways, the contributions of seminal plasma metabolites to sperm cryopreservation are still unknown. These gaps in the knowledge base are concerning because they prevent advances in the fundamental science of cryobiology and improvement of bull fertility. The objective of this study was to test the hypothesis that seminal plasma amino acids are associated with freezability of bull sperm. To accomplish this objective, amino acid concentrations in seminal plasma from seven bulls of good freezability (GF) and six bulls of poor freezability (PF) were quantified using gas chromatography–mass spectrometry (GC–MS). Multivariate and univariate analyses were performed to identify potential freezability biomarkers. Pathways and networks analyses of identified amino acids were performed using bioinformatic tools. By analyzing and interpreting the results we demonstrated that glutamic acid was the most abundant amino acid in bull seminal plasma with average concentration of 3,366 ± 547.3 nM, which accounts for about 53% of total amino acids. The other most predominant amino acids were alanine, glycine, and aspartic acid with the mean concentrations of 1,053 ± 187.9, 429.8 ± 57.94, and 427 ± 101.3 nM. Pearson’s correlation analysis suggested that phenylalanine concentration was significantly associated with post-thaw viability (r = 0.57, P-value = 0.043). Significant correlations were also found among other amino acids. In addition, partial least squares-discriminant analysis (PLS-DA) bi-plot indicated a distinct separation between GF and PF groups. Phenylalanine had the highest VIP score and was more abundant in the GF groups than in the PF groups. Moreover, pathway and network analysis indicated that phenylalanine contributes to oxidoreductase and antioxidant reactions. Although univariate analysis did not yield significant differences in amino acid concentration between the two groups, these findings are significant that they indicate the potentially important roles of amino acids in seminal plasma, thereby building a foundation for the fundamental science of cryobiology and reproductive biotechnology.

Supplementation of l-tryptophan (an aromatic amino acid) in tris citric acid extender enhances post-thaw progressive motility, plasmalemma, mitochondrial membrane potential, acrosome, and DNA integrities, and in vivo fertility rate of buffalo (Bubalus bubalis) bull spermatozoa

The aromatic amino acid l-tryptophan is an essential and versatile molecule, acts by transferring an electron to free radicals and protects the plasma membrane from injuries. The aim of the present study was to investigate the effects of l-tryptophan in extender on semen quality parameters, in vitro longevity and in vivo fertility rate of buffalo spermatozoa during cryopreservation. Two ejaculates were collected from each bull (n = 2 ejaculates and n = 4 bulls) with artificial vagina at 42 °C followed by initial evaluation for volume, motility, concentrations and were diluted in five extenders (C = lacking l-tryptophan, D1 = 25 μ M l-tryptophan, D2 = 50 μ M l-tryptophan, D3 = 75 μ M l-tryptophan, and D4 = 100 μ M l-tryptophan) respectively, and cryopreserved. The experiment was repeated four times (n = 4 replicates). At post-dilution, sperm plasma membrane integrity (PMI, %), supravital plasma membrane integrity (SVPMI, %), hypo-resistivity (HR, %) and acrosome integrity (ACR-I, %) were significantly higher (P < 0.05) in extender supplemented with D4 than control. At post-thawing, progressive motility (PM, %), PMI, SVPMI, HR, ACR-I, and DNA-I of buffalo bull spermatozoa were significantly higher in D4 than control. Sperm in vitro longevity (%) assessed in terms of PM, SVPMI, and ACR-1 were significantly higher in D4 than control. Sperm mitochondrial membrane potential (%) was higher in treated groups than the control. The in vivo fertility rate was significantly higher in D4 than control (60.17% vs. 44.17%, P < 0.05). It is concluded that the supplementation of l-tryptophan in tris citric acid extender improves semen quality parameters, in vitro longevity and in vivo fertility rate of buffalo spermatozoa during freezing and thawing process.

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

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

The CARD Method for Mouse Sperm Cryopreservation and In Vitro Fertilization Using Frozen-Thawed Sperm

In the last few years sperm cryopreservation was rapidly established as the technique to efficiently manage production, preservation, and transportation of genetically engineered mice. However, occasionally, the reduced fertility of the frozen-thawed mouse sperm can make it difficult to revitalize the mouse by in vitro fertilization (IVF). In particular, the frozen-thawed sperm of C57BL/6 mice, widely used as the background of choice for genetically engineered strains, show very low fertility after freezing and thawing. To overcome this problem, we have developed a new protocol for sperm cryopreservation and IVF with frozen-thawed C57BL/6 sperm as well as other mouse strains. This protocol has the following three modifications: (1) addition of L-glutamine to the sperm cryoprotectant, (2) addition of methyl-β-cyclodextrin to the sperm preincubation medium, and (3) addition of reduced glutathione to the fertilization medium. These modifications greatly enhanced the fertility of frozen-thawed C57BL/6 sperm, resulting in a stable fertilization rate >80% in IVF. Our results indicate that this robust protocol for sperm cryopreservation may improve the archiving and distributing system for genetically engineered mice.

Dialysis of the goat semen and its effect on the quality of frozen/thawed spermatozoa processed in the presence of egg yolk

The aim of the present study was to analyze the effect of dialysis on the quality of frozen/thawed buck semen. Ejaculates (n = 15) from three Saanen bucks were divided into three experimental groups. Semen in Group Ce (centrifugation) was processed by standard method and washed two times at 1.085 × g for 20 min. During this time, the diluted control semen (Co) was stored at room temperature. Semen in Group D was dialyzed using 300 kDa cut-off semi-permeable cellulose tubing. The semen from all groups was diluted with extender containing 20% egg yolk and frozen in liquid nitrogen vapor. After thawing, semen samples were evaluated by microscopic and biochemical analyses. Phospholipase A2 was in amounts that was 72.0 ± 11.7% less after dialysis and 21.3 ± 10.0% less after washing with centrifugation compared to the control semen (P <  0.05). Spermatozoa from Group Co had a lesser motility and viability and greater percentage of morphological abnormal spermatozoa in comparison to Groups D and Ce at 3 h after thawing and incubation on 37 °C. At the same time motility and percentage of HOST positive spermatozoa were greater in Group Ce compared with D (P <  0.05). There, however, was no difference in morphology and viability (CFDA/PI analysis) of spermatozoa between Ce and D group. Results from the present study suggest the dialysis is the promising alternative method for reducing phospholipase A2 in the buck semen before cryopreservation.

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.

Role of amino acids as additives on sperm motility, plasma membrane integrity and lipid peroxidation levels at pre-freeze and post-thawed ram semen

The possibility of including amino acids for cryopreservation of ram semen to improve the quality of frozen semen was explored in this study in sheep model. 24 samples were collected in triplicate from 8 rams of 2-3 year old Bannur cross bred rams maintained at the Institute Experimental Livestock Unit. Semen was diluted in tris-egg yolk glycerol diluent and made into 7 aliquots as follows: aliquot 1 served as control, "l-alanine" was added at 100 and 135mM in the aliquots 2 and 3, "l-glutamine" was added at 20 and 25mM in the aliquots 4 and 5 and "l-proline" was added at 25 and 50mM in the aliquots 6 and 7, respectively. Diluted semen was filled in 0.25ml French straws and frozen in LN2. Inclusion of "l-proline" and "l-glutamine" in the diluent increased the percent live sperm (P<0.001), total motility (P<0.05) and maintained higher functional membrane and acrosomal integrity (P<0.001) by decreasing lipid peroxidation (P<0.001) compared to the control group. In contrast, "l-alanine" decreased the percentage of total motility, fast progressive spermatozoa and increased (P<0.01) the percentage of immotile spermatozoa. It can be concluded that 20mM "l-glutamine" and 25mM "l-proline" can be used as semen additive to freeze ram semen as they prevented cryoinjuries to sperm and improved the pre-freeze and post-thaw semen characteristics.

Spermatozoa isolated from cat testes retain their structural integrity as well as a developmental potential after refrigeration for up to 7 days

The objective of this study was to compare the efficiency of preservation media for isolated feline testicular spermatozoa as well as the concentrations of bovine serum albumin (BSA) on: (1) the membrane (sperm membrane integrity (SMI)) and DNA integrity of spermatozoa; and (2) the developmental potential of spermatozoa after intracytoplasmic sperm injection (ICSI). Isolated cat spermatozoa were stored in HEPES-M199 medium (HM) or Dulbecco's phosphate-buffered saline (DPBS) at 4°C for up to 7 days. Results indicated that HM maintained a better SMI than DPBS throughout the storage periods (P > 0.05). When spermatozoa were stored in HM supplemented with BSA at different concentrations (4, 8 or 16 mg/ml), SMI obtained from HM containing 8 and 16 mg/ml BSA was higher than with 4 mg/ml BSA (P < 0.05). DNA integrity of spermatozoa stored in HM with 16 mg/ml BSA for 7 days was poorer than that of the fresh control, but the subsequent percentages of cleavage, morula, blastocyst produced by ICSI, as well as their average blastomere numbers of blastocysts, were similar (P > 0.05). In summary, cat spermatozoa immediately isolated from testicular tissue can be stored as a suspension in basic buffered medium at 4°C for up to 7 days. BSA supplementation into the medium improves membrane integrity of the spermatozoa during cold storage. Testicular spermatozoa stored in HM containing 16 mg/ml BSA retained full in vitro developmental potential after ICSI, similar to that of fresh controls even though DNA integrity had slightly declined.

Effect of cysteine and glutamine added to extender on post-thaw sperm functional parameters of buffalo bull

Amino acids seem to be crucial components for semen freezing extender due to antioxidant properties. Therefore, this study aimed to assess motility parameters, membrane integrity, intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and DNA damage to detect the optimum concentrations of cysteine and glutamine for buffalo semen cryopreservation. Twenty ejaculates of four buffalo bulls were diluted in tris-egg yolk extender and divided into seven equal groups consisting of cysteine (5, 7.5 and 10 mmol), glutamine (10, 15 and 20 mmol) and no additive. Supplementation of 5 and 7.5 mmol cysteine and 15 mmol glutamine in cryopreservation extender significantly increased post-thaw motility and plasma membrane integrity of spermatozoa with significant reduction in intracellular ROS when compared with control groups (P < 0.05). Cysteine at 7.5 mmol concentration elevated progressive motility and MMP, compared with control (P < 0.05). No significant differences were observed for motion patterns and DNA damage of frozen-thawed buffalo spermatozoa in extender containing amino acids. The findings of this study showed that supplementation of 7.5 mmol cysteine and 15 mmol glutamine in semen cryopreservation extender has more potential to decrease intracellular ROS, and subsequently elevate motility and membrane integrity of buffalo frozen-thawed spermatozoa.

The cryobiology of spermatozoa

The impact of successful cryopreservation of spermatozoa can be found in many fields, including agriculture, laboratory animal medicine, and human assisted reproduction, providing a cost-effective and efficient method to preserve genetic material for decades. The success of any cryobiologic protocol depends critically on understanding the fundamentals that underlie the process. In this review, we summarize the biophysical fundamentals critical to much of the research in sperm cryobiology, provide a synopsis of the development of sperm cryobiology as a discipline, and present the current state and directions for future research in sperm cryobiology in the three major areas outlined above-agriculture, laboratory animal medicine, and human clinical assisted reproduction. There is much room for new research, both empiric and fundamental, in all areas, including refinement of mathematical models, optimization of cryoprotective agent addition and removal procedures for spermatozoa from many species, development of effective, efficient, and facile cryopreservation protocols and freezing containers for agricultural sperm cryopreservation, and tailoring cryopreservation protocols for individual human samples.

Identification and cellular location of glutamine synthetase in human sperm

Glutamine synthetase (GS) catalyzes the de novo synthesis of glutamine, an amino acid that has been shown to influence sperm motility in mammals. To date, no information is available about GS content in human sperm. In this study, we have characterized the presence and cellular location of GS in fresh human normozoospermic samples. We have detected a single band corresponding to GS by Western blot. Confocal analysis has revealed GS immunoreactivity in the post-acrosomal head region. Moreover, double-labeling experiments with either F-actin or calicin have demonstrated GS confinement in the post-acrosomal region of the perinuclear theca. These data have been validated by a post-embedding ultra-structural study. The presence of GS in the post-acrosomal region of the perinuclear theca suggests that human sperm can carry out in glutamine synthesis.

Combination medium of cryoprotective agents containing L-glutamine and methyl-{beta}-cyclodextrin in a preincubation medium yields a high fertilization rate for cryopreserved C57BL/6J mouse sperm

Recently, a vast number of genetically-engineered mice have been created in various laboratories worldwide, all of which need to be effectively archived. The cryopreservation of mouse sperm provides a simple and economical means of storing the mice in mouse resource facilities. The current protocol for sperm cryopreservation using 18% raffinose pentahydrate and 3% skim milk (R18S3) has been adopted in most laboratories. In general, we can attain relatively high fertilization rates for frozen/thawed sperm in many inbred and F1 hybrid strains. However, the sperm of C57BL/6J mice shows an extremely low fertility rate after freezing and thawing (0-20%). In this study, we attempted to improve the low fertility of frozen/thawed C57BL/6J mouse sperm. Our results showed that a combination of R18S3 containing l-glutamine and methyl-beta-cyclodextrin (MBCD) in a preincubation medium dramatically increased the rate of fertilization (69.2 +/- 12.2%). Furthermore, the developmental potencies of two-cell embryos produced by frozen/thawed sperm to live young were normal (fresh: 46.0 +/- 8.2%, frozen/thawed: 51.5 +/- 11.1%). In summary, we conclude that a new method of sperm cryopreservation and in vitro fertilization using modified R18S3 with l-glutamine and MBCD in a preincubation medium yields a high fertilization rate for frozen/thawed C57BL/6J strain sperm. Furthermore, the new method provides a reliable archiving and reproducing system for genetically-engineered mice using sperm cryopreservation.