Soy lecithin replaces egg yolk for cryopreservation of human sperm without adversely affecting postthaw motility, morphology, sperm DNA integrity, or sperm binding to hyaluronate

MitoQ Preserves Epigenetic Modifications and Quality Parameters of Rooster Sperm During Cryopreservation Process

Cryopreservation in rooster semen is a helpful procedure to spread qualified semen samples for reproductive goals. Nevertheless, some post-thawed qualified semen samples showed a considerably poor fertility rate that might be related to epigenetic modifications during the cryopreservation process. This study aims to investigate the effect of the cryopreservation process in the presence of MitoQ as a mitochondrial-targeted antioxidant on epigenetic changes and other quality parameters (motility, morphology, mitochondrial activity, acrosome integrity, lipid peroxidation, DNA fragmentation, apoptosis status, and ROS concentration) of rooster sperm. The collected semen samples were divided into four groups of fresh samples and three groups that were supplemented by MitoQ 0, 10, and 100 nM and cryopreserved. The cryopreservation process reduced (p ≤ 0.05) DNA methylation, H3K9 acetylation, H3K4 methylation, motility parameters, membrane integrity, mitochondrial activity, acrosome integrity, viability, and increased (p ≤ 0.05) lipid peroxidation, DNA fragmentation, ROS concentration, and apoptotic-like changes compared to the fresh semen group. However, in frozen sperm groups, MitoQ 10 and 100 nM resulted in significant improvements (p ≤ 0.05) in the epigenetic modifications and other mentioned quality parameters compared to the control group (MitoQ 0). Generally, although the cryopreservation process reduced semen quality, using MitoQ could be useful in cryopreserved rooster semen quality.

Supplementation of lake extender with cysteamine preserves quality parameters and fertility potential of post-thawed rooster sperm during cryopreservation process

BACKGROUND

In the cryopreservation process, rooster spermatozoa are vastly sensitive to reactive oxygen species (ROS). This study aimed to investigate the effects of Lake extender supplemented via Cysteamine (CYS) on the quality and fertility characteristics of rooster semen during the cryopreservation process.

METHODS

Semen samples were collected from 10 proved Ross-308 roosters, diluted and cryopreserved in the Lake extender which contained 0, 1, 2, 4, and 8 mM of CYS (C-0, C-1, C-2, C-4, and C-8, respectively). Motility parameters, membrane integrity, abnormal morphology, mitochondrial activity, acrosome integrity, viability, apoptosis status, lipid peroxidation, DNA fragmentation, ROS concentration, as well as fertility potential were evaluated after thawing.

RESULTS

total motility and progressive motility were higher (P ≤ 0.05) in C-1 and C-2 compared to the other groups. The C-1 showed higher (P ≤ 0.05) membrane integrity, mitochondrial activity, acrosome integrity, viability, and lower (P ≤ 0.05) late apoptosis, lipid peroxidation, DNA fragmentation, and ROS concentration compared to the other groups. During fertility evaluation, C-1 presented a higher fertility rate than the control group. In cases of velocity parameters, abnormal morphology, early apoptosis, necrosis, and hatching rate, no significant difference (P > 0.05) was found.

CONCLUSION

using the optimal concentration of CYS (1 mM) in the Lake extender is useful for protecting rooster sperm during the cryopreservation process and it could be used for reproductive programs.

Enhanced cell survival in prepubertal testicular tissue cryopreserved with membrane lipids and antioxidants rich cryopreservation medium

The present study explores the advantages of enriching the freezing medium with membrane lipids and antioxidants in improving the outcome of prepubertal testicular tissue cryopreservation. For the study, testicular tissue from Swiss albino mice of prepubertal age group (2 weeks) was cryopreserved by slow freezing method either in control freezing medium (CFM; containing DMSO and FBS in DMEM/F12) or test freezing medium (TFM; containing soy lecithin, phosphatidylserine, phosphatidylethanolamine, cholesterol, vitamin C, sodium selenite, DMSO and FBS in DMEM/F12 medium) and stored in liquid nitrogen for at least one week. The tissues were thawed and enzymatically digested to assess viability, DNA damage, and oxidative stress in the testicular cells. The results indicate that TFM significantly mitigated freeze-thaw-induced cell death, DNA damage, and lipid peroxidation compared to tissue cryopreserved in CFM. Further, a decrease in Cyt C, Caspase-3, and an increase in Gpx4 mRNA transcripts were observed in tissues frozen with TFM. Spermatogonial germ cells (SGCs) collected from tissues frozen with TFM exhibited higher cell survival and superior DNA integrity compared to those frozen in CFM. Proteomic analysis revealed that SGCs experienced a lower degree of freeze-thaw-induced damage when cryopreserved in TFM, as evident from an increase in the level of proteins involved in mitigating the heat stress response, transcriptional and translational machinery. These results emphasize the beneficial role of membrane lipids and antioxidants in enhancing the cryosurvival of prepubertal testicular tissue offering a significant stride towards improving the clinical outcome of prepubertal testicular tissue cryopreservation.

Supplementation of Plant-Based Freezing Extender With Cysteamine Preserves Quality Parameters and Fertility Potential of Buck Sperm During Cryopreservation Process

Sperm cryopreservation in small ruminant is an efficient strategy to distribute spermatozoa for reproductive programmes, but this process reduces the fertility potential of frozen-thawed spermatozoa. The aim of the current research was to evaluate the impact of different concentrations of cysteamine (CYS) in soybean lecithin (SL)-based medium on postthawed buck semen quality and fertility potential. Semen samples were collected from five bucks, twice a week, then diluted in the SL-based extender containing different concentrations of CYS as follows: extender containing 0 mM (control, C0), 1 mM (C1), 2 mM (C2), 4 mM (C4) and 8 mM (C8) CYS. Motility characteristics, membrane integrity, abnormal morphology, mitochondrial activity, acrosome integrity, viability, apoptotic-like changes, lipid peroxidation, DNA fragmentation, ROS concentration, pregnancy rate and kidding rate were evaluated after freeze-thaw process. In results, C1 resulted in greater (p ≤ 0.05) total motility, progressive motility, average path velocity, membrane integrity, mitochondrial activity, acrosome integrity, viability, pregnancy rate and kidding rate compared to the other groups. Furthermore, supplementation of freezing medium with 1 mM of CYS presented lower (p ≤ 0.05) apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration compared to the other groups. On the other hand, C8 presented the least (p ≤ 0.05) total motility, progressive motility, average path velocity, membrane integrity, mitochondrial activity, acrosome integrity and viability as well as the highest (p ≤ 0.05) apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration compared to the other groups. Therefore, supplementation of freezing medium with 1 mM CYS could be a helpful strategy to protect buck's spermatozoa quality and fertility potential during cryopreservation process.

Cryopreservation of spermatozoa from black-and-gold howler monkeys (Alouatta caraya) using egg yolk-based or soy lecithin-based extenders

There are more than 200 species and subspecies of Neotropical Primates of which more than 40% are listed as threatened by the IUCN Red List of Threatened Species. Both in situ and ex situ conservation programs can benefit from the use of assisted reproductive technologies. The objective of this study was to evaluate, for the first time, cryopreservation techniques for Alouatta caraya semen. Semen samples were collected from five adult males, analyzed, and frozen in either Test-egg yolk or Test-soy lecithin-based extenders containing either 3 or 4% glycerol. Frozen-thawed samples were analyzed at 10, 40, and 80 min post-thaw. Egg yolk-based extenders were overall better than soy lecithin-based extenders. There was no significant difference between 3 and 4% glycerol in any of the parameters analyzed, however, 4% glycerol in egg yolk-based extender produced more favorable results for total motility, intact plasma membrane, lipid peroxidation, and DNA fragmentation index. This study brought novel information on semen characteristics and cryopreservation aspects for A. caraya, which can help shape future experiments to improve the outcome of frozen-thawed sperm for this and other species of Neotropical primates.

Coenzyme Q10 preserves buck's sperm quality during cryopreservation process in plant-based extender

Cryopreservation of small ruminant's semen is an effective strategy for distributing spermatozoa for reproductive programs, but this process decreases the fertility potential of post-thawed spermatozoa. The aim of this research was to assess the effect of different concentrations of CoQ10 in soybean lecithin (SL)-based extender on buck semen quality during cryopreservation process. Semen samples were collected from five bucks, twice a week, then diluted in the SL-based extender containing different concentrations of CoQ10 as follows: extender containing 0 µM (control, Q0), 0.1 µM (Q0.1), 1 µM (Q1), 10 µM (Q10) and 100 µM (Q100) CoQ10. Motion characteristics, membrane functionality, abnormal morphology, mitochondrial activity, acrosome integrity, viability, apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration were evaluated after freeze-thawing process. The Q10 resulted in greater (P≤0.05) total motility, progressive motility, average path velocity, membrane integrity, mitochondrial activity, acrosome integrity and viability compared to the other groups. Furthermore, supplementation of freezing extender with 10 µM of CoQ10 presented lower (P≤0.05) apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration compared to the other groups. Regarding to the protective effect of CoQ10 supplement during cryopreservation process, it could be explored as a potent antioxidant for cryopreservation of buck semen as it preserved the post-thawed buck sperm quality.

A longer period of epididymal sperm interaction with extender components during cryopreservation improves sperm quality, decreases the size of sperm distal cytoplasmic droplets, and changes the number of nanoparticles in the extender

While cryopreservation of cauda epididymal sperm (SpCau) allows the preservation of post-mortem bulls' gametes, the process triggers sperm damage. Although improving post-thaw sperm quality, using egg yolk extenders (EY) raises biosafety concerns which forces the use of EY-free extenders (EYFE). Since EYFE are less efficient in preserving post-thaw sperm quality, a strategy for ejaculated sperm (SpEj) frozen with EYFE is to add an Equilibrium Time (ET) step period to the cryopreservation process. However, the ET effect on the quality of SpCau cryopreserved in EYFE remains unknown. Distinct from SpEJ, SpCau physiologically displays cytoplasmic droplets (CDs) in the flagellum that may benefit cell exchange during ET. We hypothesized that using ET in SpCau cryopreserved with EYFE impacts sperm morphofunctional features, CD area, and in vitro fertility ability. Extender nanoparticles were also assessed. Following collection from the cauda epididymis of six Nellore bulls by retrograde flow, SpCau were cryopreserved in EYFE BoviFree® (Minitube, Germany) using three ET protocols: ET0 (no-ET); ET2.5 (2.5 h-ET); and ET5 (5 h-ET). SpCau from ET2.5 and ET5 showed a higher (P ≤ 0.05) percentage of motility and integrity of plasma and acrosome membranes and a smaller (P ≤ 0.05) distal CD area. There are no differences in sperm abnormalities, oxidative stress, capacitation-like events, and in vitro fertility ability. However, a better sperm recovery was found after Percoll® selection for ET2.5 and ET5. Interestingly, the number of nanoparticles in the extender decreased in post-thawed samples. In conclusion, an ET of 2.5 or 5 h is required for an efficient SpCau cryopreservation using an EYFE.

Cryopreservation of Semen in Domestic Animals: A Review of Current Challenges, Applications, and Prospective Strategies

Cryopreservation is a way to preserve germplasm with applications in agriculture, biotechnology, and conservation of endangered animals. Cryopreservation has been available for over a century, yet, using current methods, only around 50% of spermatozoa retain their viability after cryopreservation. This loss is associated with damage to different sperm components including the plasma membrane, nucleus, mitochondria, proteins, mRNAs, and microRNAs. To mitigate this damage, conventional strategies use chemical additives that include classical cryoprotectants such as glycerol, as well as antioxidants, fatty acids, sugars, amino acids, and membrane stabilizers. However, clearly current protocols do not prevent all damage. This may be due to the imperfect function of antioxidants and the probable conversion of media components to more toxic forms during cryopreservation.

Extend the Survival of Human Sperm In Vitro in Non-Freezing Conditions: Damage Mechanisms, Preservation Technologies, and Clinical Applications

Preservation of human spermatozoa in vitro at normothermia or hypothermia maintaining their functions and fertility for several days plays a significant role in reproductive biology and medicine. However, it is well known that human spermatozoa left in vitro deteriorate over time irreversibly as the consequence of various stresses such as the change of osmolarity, energy deficiency, and oxidative damage, leading to substantial limitations including the need for semen examinations, fertility preservation, and assisted reproductive technology. These problems may be addressed with the aid of non-freezing storage techniques. The main and most effective preservation strategies are the partial or total replacement of seminal plasma with culture medium, named as extenders, and temperature-induced metabolic restriction. Semen extenders consist of buffers, osmolytes, and antioxidants, etc. to protect spermatozoa against the above-mentioned adverse factors. Extended preservation of human spermatozoa in vitro has a negative effect on sperm parameters, whereas its effect on ART outcomes remains inconsistent. The storage duration, temperature, and pre-treatment of semen should be determined according to the aims of preservation. Advanced techniques such as nanotechnology and omics have been introduced and show great potential in the lifespan extension of human sperm. It is certain that more patients will benefit from it in the near future. This review provided an overview of the current knowledge and prospects of prolonged non-freezing storage of human sperm in vitro.

Determining the Optimal Dosage of Lecithin Nanoliposome in Rooster Semen Freezing Medium and Fertility Potential

Introduction: Lecithin nanoliposome (nano-LPO), with its cryoprotective properties, is considered to enhance the performance of a traditional semen cryoprotectant. Objective: To determine the optimal dose of lecithin nano-LPO added to the rooster semen extender. Materials and Methods: Semen samples collected weekly from eight broiler breeder roosters were mixed and aliquoted into five equal subsamples, during the five successive weeks. The subsamples were then diluted with a semen extender containing 0%, 0.5%, 1%, 1.5%, or 2% of lecithin nano-LPO. Post-thawed semen quality attributes, including sperm motility and velocity parameters, plasma membrane functionality, mitochondrial membrane potential (MMP), apoptosis-like changes, and fertility potential, were evaluated. Results: Total motility and velocity parameters, including curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity μm/s (VAP), straightness (STR), linearity (LIN), lateral head displacement (ALH), and wobble (WOB) were quadratically (p < 0.01) influenced by graded levels of lecithin nano-LPO, such that the highest values were obtained when 1% of lecithin nano-LPO was used. Treatments had no significant effect on plasma membrane functionality; however, MMP (p < 0.08) and percentages of live and dead spermatozoa (p < 0.05) quadratically responded to increasing levels of lecithin nano-LPO, where the best outcome was found when about 1% of lecithin nano-LPO was used in the semen extender. The percentage of apoptotic spermatozoa cubically responded to increasing levels of lecithin nano-LPO (p ≤ 0.07). No significant trend of fertility rate was found in response to addition of lecithin nano-LPO levels. Conclusions: Supplementing an extender with 1.10% of lecithin nano-LPO is shown to be the optimal dose associated with the most improvement in post-thawed rooster sperm velocity measurements.

Cholesterol-Loaded Cyclodextrin Addition to Skim Milk-Based Extender Enhances Donkey Semen Cooling and Fertility in Horse Mares

The present study aimed to compare semen parameters and fertility of cooled donkey semen extended in a commercially available skim milk (SKM) based extender and the same extender with cholesterol-loaded cyclodextrin (SKM-CLC). In Experiment 1, thirty-five ejaculates from seven jacks were split in SKM and SKM-CLC, extended at 50 million sperm/mL and stored at 5°C for 48 hours. Total motility (TM), progressive motility (PM), percentage of sperm with rapid motility (RAP) were assessed with CASA. Plasma membrane stability (PMS), and high mitochondrial membrane potential (HMP) were assessed with the combination of Yo-Pro and MitoStatusRed with flow cytometry. Semen was assessed before (0), 24 and 48h after cooling. In Experiment 2, two estrous cycles of 15 mares were used for fertility assessment. Mares were examined every other day by transrectal ultrasonography and had ovulation induced with 250 µg of histrelin acetate when a ≥35 mm follicle was first detected. Mares were randomly inseminated with semen obtained from one jack. Semen was extended in either SKM or SKM-CLC and cooled-stored for 24 hours. Pregnancy diagnosis was carried out 15-day post-ovulation. Data were analyzed with a mix model and Tukey's as posthoc and logistic regression model. Significance was set at P ≤ .05. There were no differences in TM, PM, RAP, PMS, and HMP for semen extended in either extender immediately before cooling (P > .05). There was a reduction in TM, PM, RAP, PMS, and HMP overtime across groups (P < .05); however, semen extended with SKM-CLC had superior TM, PM, RAP, PMS, and HMP than semen extended in SKM at 24- and 48-hours post-cooling (P < .05). Mares bred with semen extended in SKM had a lower conception rate (13%, 2/15 cycles) than cycles bred with SKM-CLC (47%, 7/15 cycles; P < .05). In conclusion, incorporating CLC into SKM extender improved cooling ability and fertility of donkey semen in horse mares. It remains to be determined if similar results can be obtained in clinical practice with mares and jennies.

Phosphatidylcholine and L-acetyl-carnitine-based freezing medium can replace egg yolk and preserves human sperm function

Background

Conventional cryopreservation methods induce chemical and mechanical damage to the sperm membranes. The cryoprotectant potential of phospholipids of vegetal origin as soybean lecithin has been investigated as a substitute for egg yolk in diluents used for the cryopreservation of human spermatozoa. Therefore, the objective of this study was comparing the efficacy of a synthetic cryoprotectant supplemented with L-α-phosphatidylcholine (PC) and L-acetyl-carnitine (ANTIOX-PC) and the standard egg-based TEST-yolk buffer (TYB) in preserving sperm motility and chromatin quality in cryopreserved semen samples.

Methods

Prospective experimental study in which semen samples from 63 men with normal sperm motility and 58 men with low sperm motility were included and analyzed both before and after cryopreservation using ANTIOX-PC or TYB freezing media. Sperm quality was evaluated by routine semen analysis and DNA fragmentation index using the Terminal deoxynucleotidyl transferase dUTP nick end labeling assay.

Results

Differences in the post-thaw progressive motility and DNA fragmentation index were not detected between TYB and ANTIOX-PC cryoprotectants in both normal and low sperm motility groups (P>0.05). However, ANTIOX-PC medium retained higher non-progressive motility and lower percentage of immotile sperm when compared to TYB medium, resulting in a greater total motile sperm count (P<0.05), regardless baseline values of motility characteristic of the normospermic or asthenozoospermic samples.

Conclusions

ANTIOX-PC medium was effective to protect human sperm during a freeze-thaw cycle compared to the TYB medium. A clinically relevant advantage in better preserving kinetic parameters as higher total motility and lower immotile post-thawed sperm from ANTIOX-PC, in normal and low motility semen samples, demonstrated the positive impact of phospholipid and antioxidant treatment on sperm cryotolerance with high potential for egg yolk lipids replacement and biosafety.

Cross-species efficacy of a chemically-defined, soy lecithin-based cryomedium for semen banking in imperiled wild felids

Felid semen has historically been frozen using an egg yolk-based cryopreservation medium. However, the use of egg introduces several potential concerns, such as variability in composition, microbial contamination, and regulatory issues. In the present study, our aim was to compare a chemically-defined, soy-based medium (SOY) to a commercial egg yolk-based medium (TEY) for the cryopreservation of sperm in four imperiled small cat species. Semen was collected from adult male cats (n = 6 black-footed cats; n = 6 sand cats; n = 4 fishing cats; and n = 7 Pallas' cats) via electroejaculation, split into two aliquots, and cryopreserved in SOY or TEY. Frozen-thawed samples were evaluated for sperm motility and rate of progressive motility (up to 24 h post-thaw) and acrosome status (0 and 6 h). No difference in post-thaw traits were observed between treatments in all four species. Heterologous IVF using oocytes collected laparoscopically from domestic cats demonstrated no difference among freezing treatments in percentage of mature oocytes that cleaved or the mean number of blastomeres at 48 h post-insemination. More spermatozoa frozen with SOY were bound to the zona pellucida in the sand cat (P = 0.018), but no treatment effect was observed in the other three species. These findings collectively demonstrate that SOY may be a preferable alternative to TEY for sperm cryopreservation in these four wild felid species.

Ram semen preserved at 0°C with soybean lecithin Tris-based extender substituted for egg yolk

OBJECTIVE

The present study evaluated the preservation of ram semen at 0°C using soybean lecithin with a Tris-fructose extender.

METHODS

Semen was collected by artificial vagina ejaculation from six rams with proven fertility. High quality ejaculates were diluted by soybean lecithin (0.25%, 0.5%, 0.75%, 1.0%, 1.25%) using Tris-fructose extender and control (Tris-fructose egg yolk extender), respectively. The ejaculates were diluted to a concentration of 5×108 sperm/mL, followed by cooling to 0°C in 90 min and maintaining the temperature for 12 days. The diluted semen samples were examined and recorded for sperm progressive motility, acrosome integrity at 0, 24, 72, 144, 216, 288 h, respectively. Two hundred and twenty-three ewes were inseminated for 216 h with optimal soybean lecithin concentrated semen or control via trans-cervical insemination.

RESULTS

The results showed that there were no differences in sperm progressive motility at 0, 24, 72, and 144 h (p>0.05). After 216 h, the sperm progressive motility in the control group and 0.5% concentration groups was significantly higher when compared to 0.25% concentration (p<0.05). The 0.5% concentration group demonstrated the highest survival rate and had no difference with the control group (p>0.05). At 216 h, the sperm progressive motility of all groups was still above 50%. The acrosome integrity of all groups was decreased with prolongation of storage time, but there was no difference at each time point (p>0.05). There was no significant difference in the lambing rate and pregnancy rate between the 0.5% concentration group and the control group (p>0.05).

CONCLUSION

These results suggest that ram sperm is capable of fertilization after preservation at 0°C with 0.5% of soybean lecithin in Tris-based extender substituted for egg yolk and produce normal offspring after insemination.

Effects of CoQ10 on the quality of ram sperm during cryopreservation in plant and animal based extenders

The purpose of this study was to evaluate the effect of different concentrations of CoQ10 in soybean lecithin (SL) or egg yolk (EY) extenders on ram semen cryopreservation. Semen samples were collected from five rams, twice a week, then diluted in the extenders (SL and EY) containing different concentrations of CoQ10 as follows: extender containing SL: 0 μM (control, SL/Q0), 1 μM (SL/Q1), 2 μM (SL/Q2), 5 μM (SL/Q5) and 10 μM (SL/Q10) CoQ10; extender containing EY: 0 μM (control, EY/Q0), 1 μM (EY/Q1), 2 μM (EY/Q2), 5 μM (EY/Q5) and 10 μM (EY/Q10) CoQ10. Sperm motion characteristics, membrane integrity, abnormal morphology, viability, apoptotic-like changes, mitochondria active potential, acrosome integrity and lipid peroxidation were evaluated after freeze-thaw process. The SL/Q1, SL/Q2, EY/Q1 and EY/Q2 resulted in greater (P ≤ 0.05) sperm total motility, progressive motility, membrane integrity and mitochondria active potential compared to the other groups. Acrosome integrity in the SL/Q0, SL/Q1, SL/Q2, EY/Q0, EY/Q1 and EY/Q2 groups was greater (P ≤ 0.05) than in the SL/Q5, SL/Q10, EY/Q5 and EY/Q10 groups. The SL/Q2 and EY/Q2 treatment groups had greater (P ≤ 0.05) sperm viability rates and less apoptotic-like changes and lipid peroxidation. The CoQ10 compound could be explored as a novel potential antioxidant for cryopreservation of ram semen because with used of this compound in the present study there was an improved post-thawed sperm quality.

Efficacy of soy-lecithin for replacing egg yolk in tris extender on quality of frozen buck semen

The present study undetaken to find the efficacy of incorporating soy-lecithin in tris extender for replacing egg yolk, a widely used animal component. Pooled ejaculates (40), 10 from each of four bucks maintained at Goat Research Station, Burnihat were used for freezing in tris extender containing 1% and 1.5% soy-lecithin and 20% egg yolk by adopting split sample technique following conventional method. The post thaw sperm motility in 1.5% soy-lecithin-tris extender (60.20±0.45%) was comparable with that of 20% egg yolk-tris (61.20±0.45%), the difference being non-significant. However, the post thaw values for live sperm, intact acrosome and hypo-osmotic swollen sperm were significantly lower in 1.5% soy-lecithin-tris as compared to that in 20% egg yolk-tris. The post thaw values were significantly higher for 1.5% than that for 1% soy-lecithin for all the parameters studied. It could be concluded that 1.5% soy-lecithin-tris extender has similar efficacy with that of 20% egg yolk-tris extender in respect of post thaw sperm motility; however, significantly lower post thaw values for remaining sperm qualities obtained with soy-lecithin in tris-based extender necessitate further trials comprising higher number of ejaculates from more bucks to find a suitable level of soy-lecithin for replacing egg yolk in tris extender for freezing of goat semen.

Insights into soy lecithin and egg yolk-based extenders for chilling canine spermatozoa

SummaryThe aim of this study was to compare different concentrations of soy lecithin (LEC0.01%, LEC0.05% and LEC0.1%) with egg yolk (Control) in cooling extenders during the storage of semen at 5ºC for 5 days. Twelve dogs (n = 12) were selected, and semen was cooled and assessed after 2, 24, 48, 72, 96 or 120 h. At each time point, sperm were analyzed for kinetic patterns (using computer-assisted sperm analysis), mitochondrial activity (3'3- diaminobenzidine assay), lipid peroxidation (TBARS assay), DNA fragmentation (SCSA®) and plasma and acrosome membrane integrity (eosin/nigrosin and fast green/rose Bengal stains, respectively). The Control group (1814.4 ± 197.2) presented the highest rates of lipid peroxidation at 120 h. Conversely, progressive motility (42.8 ± 4%), linearity (45.4 ± 1%), and VAP (88 ± 3%) were higher in the Control group. In addition, there was lower mitochondrial activity in the Control group at 72 h. Therefore, our data show that lecithin used at these concentrations was not able to maintain sperm viability at as high qualities as would egg yolk. Moreover, the decrease in high mitochondrial activity and the persistence of sperm motility may indicate a compensatory mechanism in canine spermatozoa (i.e., glycolytic pathway). Furthermore, these higher lipid peroxidation indexes could indicate the necessity for future therapy using extenders and antioxidants over a long cooling time for dog sperm.

Comparison of soy lecithin, coconut water, and coconut milk as substitutes for egg-yolk in semen cryodiluent for black rhinoceros (Diceros bicornis) and Indian rhinoceros (Rhinoceros unicornis)

Semen cryopreservation for the black rhinoceros (Diceros bicornis) and Indian rhinoceros (Rhinoceros unicornis) relies on extenders containing egg-yolk (EY). Use of such media is not ideal as inter-batch composition varies and there is risk of pathogenic contamination. The goal of this study was to test animal protein-free extenders. Semen collected via electroejaculation from 10 rhinoceros (6 black, 4 Indian) was diluted with extender containing EY, 1% or 2% soy lecithin (1%SL; 2%SL), coconut water (CW), or coconut milk (CM), cryopreserved and evaluated for sperm motility, viability, morphology, progression, and acrosomal integrity at 0, 1, 3, 6 and 24 h post-thaw. Mean ± SD fresh ejaculate motility was 84.5 ± 7.6%, progression: 3.6 ± 0.6 (scale 0-5), viability: 83.4 ± 7.1%, intact acrosomes: 71.3 ± 6.9%, and morphologically normal: 78.8 ± 13.6%. Motility and progression decreased in all groups post-thaw, were greatest in EY, and decreased over time (P ≤ 0.05). Motility and progression did not differ (P > 0.05) between 1%SL and 2%SL, but were lower (P ≤ 0.05) in CM and CW, and acrosomal integrity was higher (P ≤ 0.05) in EY, 1%SL and 2%SL than in CM and CW. Post-thaw viability was greatest in EY and 2%SL followed by 1%SL, then CM and CW (P ≤ 0.05). Morphology did not differ among treatments (P > 0.05). Morphology, acrosomal integrity, and viability were maintained over time (P > 0.05). Although some rhinoceros sperm survived cryopreservation in SL treatments, reduced post-thaw motility rendered all treatments inadequate substitutes for EY-based extenders.

Effects of Soy Lecithin Extender on Dog Sperm Cryopreservation

Semen cryopreservation is an essential biotechnology in canine reproduction and during the cryopreservation process commonly egg yolk are used. The discrepancy in the egg yolk composition and the potential risk of disease dissemination are obstacles for semen exportation and use. Therefore, studies aiming to substitute egg yolk are extremely important. In this context, soy lecithin contains a low-density lipoprotein fraction, is an interesting alternative. Thus, the objective of this study was to compare extenders based on soy lecithin (several concentrations and forms) with egg yolk during the cryopreservation process of dog sperm. For this purpose, we used twelve dogs. Semen was evaluated at different time points (after refrigeration, glycerolization, and thawing), by motility analysis (CASA) and functional tests (e.g., membrane integrity-eosin/nigrosin, acrosome integrity-fast green/Bengal rose, mitochondrial activity-3'3 diaminobenzidine, Chromatin susceptibility to acid-induced denaturation-SCSA, and susceptibility to oxidative stress-thiobarbituric acid reactive substances). The results indicated that egg yolk and lower concentrations of lecithin had similar effects on mitochondrial activity and motility. Thus, soy lecithin is a potentially viable alternative to egg yolk for the cryopreservation of dog semen.

Effect of sunflower lecithin on Kalahari Red goat semen during cryopreservation

Soybean lecithin had been used as an alternative to egg yolk in domestic animal semen extender during cryopreservation due to its characteristic phospholipid content which played a major cryoprotective role. This composition of soybean lecithin informed the replacement of soybean with sunflower lecithin (SL) in the extender for the Kalahari Red (KR) buck semen cryopreservation in this study. Effect of different levels of SL on the quality of the KR buck semen during cryopreservation using slow freezing method was evaluated. Semen samples were collected from four KR bucks of between two and two and half of age using artificial vagina, evaluated for motility and then diluted in extenders containing different levels of SL (1.5%, 3.0% and 4.5%) as experimental group and 0% SL or 20% egg yolk as control. Semen parameters including motility, acrosome integrity (AcI), membrane integrity (MI), malondialdehyde (MDA) concentration, cholesterol level and seminal arginase activity were evaluated for. The results showed that motility, acrosome integrity (AI) and membrane integrity were comparable at 0%, (22.00 ± 4.58, 82.00 ± 3.51 and 96.00 ± 2.03); 1.5%, (23.00 ± 2.08, 87.00 ± 3.79 and 89.00 ± 2.08); 3.0%, (13.00 ± 2.52, 81.33 ± 0.41 and 76.67 ± 1.20) and 4.5% (11.00 ± 4.51, 85.33 ± 9.88 and 84.00 ± 8.50), respectively, after thawing. SL at 0% had the highest (P < 0.05) values for MDA, cholesterol and seminal arginase activity (1.10 ± 0.008 nmol/ml, 236.35 ± 4.08 mg/dl and 0.54 ± 3.3 E-3 units/mg protein, respectively). Our data suggest that 1.5% sunflower lecithin can be used in place of soy lecithin as a substitute for egg yolk during the cryopreservation of caprine semen.

Cryopreservation of bull semen: Evolution from egg yolk based to soybean based extenders

Since the inception of bovine semen cryopreservation, egg yolk and milk based extenders have been used to protect sperm from the detrimental effects of cooling and freezing. In recent years, demand for alternatives to conventional commercial extenders has arisen as the risk of introducing exotic diseases through transporting egg yolk based products has been recognized. Egg yolk can also interfere with sperm evaluation and the presence of particulate material in the extender may reduce fertility. Soybeans contain lecithin, a phospholipid fraction that can substitute for high molecular weight lipoprotein and phospholipids from egg yolk and prevent or ameliorate damage to the sperm plasma membrane that occurs during extension, cooling, and cryopreservation. Soy lecithin based extenders have been evaluated for processing and freezing bovine semen, although extender from soybean milk has not been studied as extensively. Commercially available soy lecithin based extenders are used increasingly but remain under scrutiny and are not universally accepted. With these observations in mind, this review is intended to examine effects of conventional cryopreservation procedures, methods of assessment, and potential for developing soybean extract as an acceptable alternative to traditional egg yolk and milk based extenders for bull sperm cryopreservation.

Fertility and flow cytometry study of frozen-thawed sperm in cryopreservation medium supplemented with soybean lecithin

Semen cryopreservation can provide genetic resources for a large number of females from a small number of superior males. Optimization of cryopreservation media to achieve the highest quality of post-thaw semen is crucial. Soybean lecithin has evaluated as a plant-based cryoprotectant for substitution of egg yolk in ram semen extender. Flow cytometric and fertility assessments were applied following cryopreservation procedure in two experimental groups (SL group: extender containing 1% w/v soybean lecithin and EY group: extender containing 20% v/v egg yolk). The higher percentage of live sperm and the lower percentage of dead sperm were obtained in SL (47.66 ± 1.38, 52.33 ± 1.69, respectively) extender compared to EY (41.16 ± 1.38, 58.83 ± 1.69). For motion characteristics, plasma membrane integrity, acrosome integrity and mitochondria activity, no significant difference was observed between SL and EY extenders. In artificial insemination experiment, there was no significant difference in pregnancy rate, lambing rate and twining rate between SL and EY extenders. It can be concluded that SL extender can be an efficient alternative extender to preserve ram sperm during cryopreservation procedure without adverse effects.

Effects of n-6 and n-3 polyunsaturated acid-rich soybean phosphatidylcholine on membrane lipid profile and cryotolerance of human sperm

OBJECTIVE

To study the effects of n-6 and n-3 polyunsaturated acid-rich soybean phosphatidylcholine (soy-PC) on sperm cryotolerance with regard to sperm membrane lipid profile, membrane surface integrity, and routine semen parameters.

DESIGN

Experimental study.

SETTING

University-affiliated tertiary hospital.

PATIENT(S)

A total of 20 normospermic fertile men.

INTERVENTION(S)

Semen samples examined for differences in semen parameters, sperm membrane lipid profile, and plasma membrane surface both before and after cryopreservation using basic freezing medium with N-tris(hydroxymethyl)-methyl-2-aminoethane sulfonic acid (TES) and tris-(hydroxymethyl)-aminomethane (TRIS) supplemented with purified soy-PC (TEST-PC) or egg yolk (TEST-Y), both alone or in association (TEST-Y-PC).

MAIN OUTCOME MEASURE(S)

Conventional semen parameters and membrane lipid profile by matrix-assisted laser/desorption ionization mass spectrometry (MALDI-MS).

RESULT(S)

Postthaw sperm cell motility, vitality, and morphology parameters were similar for soy-PC (TEST-PC) and egg yolk (TEST-Y) cryoprotectants. However, sperm exposed to TEST-Y-PC presented better kinetic parameters, which were similar to the original quality of the fresh semen. Human sperm MALDI-MS lipid profiles revealed that the relative abundance of glycerophospholipids of m/z 760.44 [PC (34:1)+H]+, 781.55 [SM (20:0) +Na]+, 784.55 [PC (36:3) +H]+, 806.64 [PC (38:6) +H]+, 807.64 [SM (22:1) +Na]+, and 809.64 [SM (22:0) +Na]+ increased in soy-PC samples (TEST-PC). Nonetheless, only one lipid (m/z 781.55, [SM (20:0) +Na]+) statistically significantly changed when sperm was cryopreserved in TEST-Y-PC.

CONCLUSION(S)

Sphingomyelin was defined as a prospective biomarker of soy-PC treatment, and it could be related to the positive cryoprotective effects of soy-PC in human sperm, opening new perspectives to design of a more efficient synthetic cryoprotectant medium containing purified egg yolk biomolecules combined with soy-PC.

Sperm cryopreservation update: Cryodamage, markers, and factors affecting the sperm freezability in pigs

Cryopreservation is the most efficient method for long-term preservation of mammalian sperm. However, freeze-thawing procedures may strongly impair the sperm function and survival and thus decrease the reproductive performance. In addition, the sperm resilience to withstand cryopreservation, also known as freezability, presents a high individual variability. The present work summarizes the principles of cryoinjury and the relevance of permeating and nonpermeating cryoprotective agents. Descriptions about sperm cryodamage are mainly focused on boar sperm, but reference to other mammalian species is also made when relevant. Main cryoinjuries not only regard to sperm motility and membrane integrity, but also to the degradation effect exerted by freeze-thawing on other important components for sperm fertilizing ability, such as mRNAs. After delving into the main differences between good and poor freezability boar ejaculates, those protein markers predicting the sperm ability to sustain cryopreservation are also mentioned. Moreover, factors that may influence sperm freezability, such as season, diet, breed, or ejaculate fractions are discussed, together with the effects of different additives, like seminal plasma and antioxidants. After briefly referring to the effects of long-term sperm preservation in frozen state and the reproductive performance of frozen-thawed boar sperm, this work speculates with new research horizons on the preservation of boar sperm, such as vitrification and freeze-drying.

Motility and fertility of rabbit sperm cryopreserved using soybean lecithin as an alternative to egg yolk

This study was conducted to investigate whether soy lecithin can be used as an alternative cryoprotectant to establish a procedure that does not require the use of egg yolk to cryopreserve rabbit strains. Semen from Japanese White rabbits was frozen with HEPES extender containing 20% egg yolk (EYH), 0.5% (Lec-0.5), 1.5% (Lec-1.5), 2.5% (Lec-2.5), or 3.5% (Lec-3.5; wt/vol) lecithin (type IV-S, ≥30%), and the motility of thawed sperm was analyzed. The sperm motility in the Lec-1.5 group was significantly higher than that in the Lec-2.5 and 3.5 groups and equivalent to the EYH group. From 17 rounds of artificial insemination with frozen-thawed sperm in the EYH and Lec-1.5 groups, 12 rabbits in both groups were pregnant (70.6%) and delivered offspring. The litter size was 3.3 in the EYH group and 5.1 in the Lec-1.5 group. These results indicate that soy lecithin can be used as a substitute for egg yolk as a cryoprotectant on the basis of motility and fertility of the frozen-thawed rabbit sperm and that 1.5% lecithin (type IV-S, ≥30%) in the semen extender was the optimum concentration for rabbit sperm cryopreservation.

Flow cytometric and microscopic evaluation of post-thawed ram semen cryopreserved in chemically defined home-made or commercial extenders

The present study was designed to determine the effect of three different extenders on ram sperm quality during a freeze–thawing procedure using flow cytometric and microscopic evaluations. Several in vitro qualitative analyses of post-thawed sperm parameters including motility and velocity parameters, plasma membrane functionality, total abnormality, capacitation status, acrosome integrity, mitochondrial activity and apoptosis features were considered. In the breeding season, seven ejaculates from each Zandi ram were collected routinely twice a week. Following semen collection, samples were pooled and equally divided into three aliquots. Each aliquot was diluted and frozen with one of the following extenders: (1) Tris-based extender containing 1.5% (w/v) soybean lecithin (TSL), as a chemically defined extender, (2) Bioxcell, a commercial soybean lecithin-based extender, and (3) Tris-based extender containing 20% (v/v) egg yolk (TEY). The results of the present study indicated no differences in total [TSL (55.8 ± 2.02%) vs TEY (50.2 ± 2.02%; P < 0.05)] and progressive motility of spermatozoa [TSL (26.2 ± 1.36%) vs Bioxcell (22.4 ± 1.36%; P < 0.05)]. Semen freezing by means of TSL resulted in a higher percentage of live spermatozoa (39.42 ± 1.81%) compared with TEY (29.17 ± 1.81%; P < 0.05), and a higher percentage of functional plasma membrane (50.8 ± 192%) compared with TEY (44 ± 1.92%) and Bioxcell (38.8 ± 1.92%; P < 0.05). The effect of extenders on sperm capacitation status showed that the percentage of post-thawed capacitated spermatozoa was higher in TEY (61.9 ± 1.48%) compared with that in TSL (56.6 ± 1.48%; P < 0.05). The evaluation of post-thawed spermatozoa indicated that the percentage of live spermatozoa with active mitochondria was higher in TSL (53.05 ± 2.31%) compared with Bioxcell (45.92 ± 2.31; P < 0.05) and the percentage of intact acrosome spermatozoa was higher in TSL (84.55 ± 2.51%) compared with TEY (74.91 ± 2.51%; P < 0.05). The use of TSL and Bioxcell extenders reduced the percentage of apoptotic spermatozoa (40.82 ± 2.07% and 42.22 ± 2.07%, respectively), compared with TEY (51.34 ± 2.07%; P < 0.05). Post-thawing dead spermatozoa were increased when semen was frozen by Bioxcell (25.69 ± 1.28%). The results of this study showed that TSL extender may provide stabile milieu and conditions for ram sperm cryopreservation compared with Bioxcell and TEY extenders. Whether TSL extender can improve the artificial insemination results remains, however, an open question.

Soybean lecithin-based extender preserves spermatozoa membrane integrity and fertilizing potential during goat semen cryopreservation

Soybean lecithin may represent a suitable alternative to egg yolk for semen cryopreservation in livestock species. However, additional studies are needed to elucidate its effects on spermatozoa functional properties. Semen collected from five Sarda bucks was cryopreserved in Tris-based extender and glycerol (4% v:v) with different supplementations. In a preliminary experiment, different soybean lecithin concentrations were tested (1%-6% wt/vol) and results in terms of viability, percentages of progressive motile and rapid spermatozoa, and DNA integrity after thawing showed that the most effective concentration was 1%. In the second experiment, semen was frozen in a Tris-based extender with no supplementation (EXT), with 1% lecithin (EXT LC), and 20% egg yolk (EXT EY). The effectiveness of these extenders was also compared with a commercial extender. The EXT EY led to the highest viability and motility parameters after freezing and thawing (P < 0.0001). No significant differences were observed in intracellular ATP concentrations. Additional molecular features revealed that sperm functionality was affected in EXT EY, as demonstrated by lower DNA and acrosome integrity (P < 0.05), and higher lipid peroxidation compared with spermatozoa cryopreserved in EXT LC (P < 0.0001). Results obtained in the heterologous in vitro fertilization test showed that EXT LC better preserved spermatozoa functionality, as demonstrated by the higher fertilization rates compared with the other media (66.2 ± 4.5% for EXT LC vs. 32.7 ± 4.5%, 38.7 ± 4.5%, 39.6 ± 5.2% for EXT, EXT EY, and commercial extender; P < 0.01). The present study demonstrated that lecithin can be considered as a suitable alternative to egg yolk in goat semen cryopreservation, because it ensures higher fertilization rates and a better protection from membrane damage by cold shock.

Liposome encapsulated soy lecithin and cholesterol can efficiently replace chicken egg yolk in human semen cryopreservation medium

Cryopreservation of spermatozoa plays a significant role in reproductive medicine and fertility preservation. Chicken egg yolk is used as an extender in cryopreservation of human spermatozoa using glycerol egg yolk citrate (GEYC) buffered medium. Even though 50% survival of spermatozoa is generally achieved with this method, the risk of high levels of endotoxins and transmission pathogens from chicken egg yolk is a matter of concern. In the present study we attempted to establish a chemically defined cryopreservation medium which can replace the chicken egg yolk without affecting sperm survival. Ejaculates from 28 men were cryopreserved with GEYC based freezing medium or liposome encapsulated soy lecithin-cholesterol based freezing medium (LFM). The semen samples were subjected to rapid thawing after 14 days of storage in liquid nitrogen. Post-thaw analysis indicated significantly higher post-thaw motility and sperm survival in spermatozoa cryopreserved with LFM compared to conventional GEYC freezing medium. The soy lecithin and cholesterol at the ratio of 80:20 with sucrose showed the highest percentage of post-thaw motility and survival compared to the other compositions. In conclusion, chemically defined cryopreservation medium with liposome encapsulated soy lecithin and cholesterol can effectively replace the chicken egg yolk from human semen cryopreservation medium without compromising post-thaw outcome.

In vitro assessment of soybean lecithin and egg yolk based diluents for cryopreservation of goat semen

Soybean lecithin is a suitable plant-based cryoprotectant for freezing ruminant sperm. Optimum level of lecithin was not clear for goat semen cryopreservation. The objective of this study was to investigate the effects of different levels of soybean lecithin in semen extender on post-thaw sperm quality including CASA-motion parameters, viability, plasma membrane integrity and lipid peroxidation. Semen samples were collected from 4 Mahabadi bucks using an artificial vagina. Different concentrations of soy lecithin (SL, 0.5%, 1%, 1.5%, 2% and 2.5% w/v) were compared to 15% (v/v) egg yolk-based extender (TR-EY). No significant difference was observed for sperm progressive motility, viability or plasma membrane integrity in 1.5% SL media (33.8%, 66%, and 62.7%, respectively) and TR-EY medium (35.4%, 67.2%, and 64.9%, respectively). Sperm motion characteristics (VAP, VSL, VCL, ALH and LIN) and rapid spermatozoa were improved with extender containing 1% and 1.5% SL, compared to TR-EY extender. Furthermore, egg yolk produced significantly higher malondialdehyde (4.02±0.21) than other groups. Results suggest that the optimal lecithin concentration in the semen extender was 1.5% and also soy lecithin can substitute for egg yolk during cryopreservation for caprine sperm.

Epididymosomes, prostasomes, and liposomes: their roles in mammalian male reproductive physiology

Mammalian spermatozoa are unique cells in many ways, and the acquisition of their main function, i.e. fertilization capacity, is a multistep process starting in the male gonad and ending near the female egg for the few cells reaching this point. Owing to the unique character of this cell, the molecular pathways necessary to achieve its maturation also show some specific characteristics. One of the most striking specificities of the spermatozoon is that its DNA is highly compacted after the replacement of histones by protamines, making the classical processes of transcription and translation impossible. The sperm cells are thus totally dependent on their extracellular environment for their protection against oxidative stress, for example, or for the molecular changes occurring during the transit of the epididymis; the first organ in which post-testicular maturation takes place. The molecular mechanisms underlying sperm maturation are still largely unknown, but it has been shown in the past three decades that extracellular vesicles secreted by the male reproductive tract are involved in this process. This review will examine the roles played by two types of naturally occurring extracellular vesicles, epididymosomes and prostasomes, secreted by the epididymis and the prostate respectively. We will also describe how the use of artificial vesicles, liposomes, contributed to the study of male reproductive physiology.

Soy lecithin interferes with mitochondrial function in frozen-thawed ram spermatozoa

Egg yolk and milk are the 2 major membrane cryoprotectants commonly used in freezing media for the long-term preservation of semen (alone or in combination with others). However, in recent years, there have been increasing arguments against the use of egg yolk or milk because of the risk of introducing diseases through the use of cryopreserved semen. In this study, we analyzed the protective effect of lecithin as an alternative to egg yolk for the cryopreservation of ram semen, using a range of functional markers for sperm viability, motility, apoptosis, and mitochondrial functionality analyses (mitochondrial inner membrane surface [MIMS], mitochondrial inner membrane potential [MIMP], and cell membrane potential) as methods of assessment in samples diluted in 3 different media: Tris-citrate-glucose as control and 2 media supplemented with soy lecithin or egg yolk. The results showed that lecithin was able to effectively protect certain sperm quality characteristics against freezing-induced damage. However, lecithin induced loss of mitochondrial membrane potential or mitochondrial loss that was not reflected by modifications in sperm motility in fresh semen. MIMS and MIMP values decreased in thawed lecithin-treated samples, concomitant with a lower (P < .05) percentage of total and progressively motile cells, compared with those in egg yolk-containing samples. Further incubation of thawed samples revealed changes in motility and mitochondrial functionality that otherwise would not have been detected. These results indicated that lecithin may have affected the inner mitochondrial membrane in frozenthawed spermatozoa and confirmed that sublethal damages that seriously affect sperm functionality, not detected by classic sperm quality analyses, can be evidenced by changes in the inner mitochondrial membrane surface. These findings strengthen the relationship between mitochondrial membrane potential and motility and show that the mitochondrial alterations induced by the cryopreservation process could be specific targets for the improvement of semen cryopreservation protocols.

Dissecting the molecular damage to stallion spermatozoa: the way to improve current cryopreservation protocols?

We review recent developments in the technology of freezing stallion sperm, paying special attention to the molecular lesions that spermatozoa suffer during freezing and thawing, such as osmotic stress, oxidative damage, and apoptotic changes. We also discuss the applicability of colloidal centrifugation in stallion sperm cryobiology. Increased knowledge about the molecular injuries that occur during cryopreservation may lead to improved protective techniques and thus to further improvements in fertility in the current decade.

Cryopreservation and oxidative stress in reproductive cells

In spite of the optimisation of cryopreservation protocols, post-thawing trauma to mammalian gametes cannot be completely avoided. Based on recent literature, cellular cryodamage in reproductive cells has been extensively characterised in terms of changes in the cell structure, whereas biochemical alterations have been poorly investigated. The present paper reviews the current knowledge about the involvement of oxidative stress in frozen-thawed cells by considering the most relevant studies in sperm and oocytes. Recognising that spermatozoa are highly susceptible to oxidative damage induced by cryopreservation, the need for further research is highlighted in order to understand whether changes in the redox state have a role in the reduced developmental potential of cryopreserved human reproductive cells.