Effects of cryopreservation on sperm quality, nuclear DNA integrity, in vitro fertilization, and in vitro embryo development in the mouse

Effect of quercetin and mirtazapine on spermatogenesis and testis structure in phenylhydrazine-induced hemolytic anemia mice: An experimental study

Anemia poses a significant healthcare challenge across different socioeconomic groups and can result in reproductive system damage through the generation of free radicals and lipid peroxidation. This study examines the protective effects of quercetin (QUE) and mirtazapine (MIR) against the reproductive damage caused by phenylhydrazine (PHZ) in mice. Fifty NMRI mice, aged 8-10 weeks with an average weight of 27.0 ± 2.0 g, were randomly divided into five groups. The control group (Group 1) received oral administration of 10 mL/kg/day of normal saline. Group 2 (PHZ group) received an initial intraperitoneal dose of 8 mg/100 g body weight of PHZ, followed by subsequent doses of 6 mg/100 g every 48 h. Group 3 received PHZ along with oral QUE at a dosage of 50 mg/kg/day. Group 4 received PHZ along with oral MIR at a dosage of 30 mg/kg/day. Group 5 received PHZ along with oral QUE at a dosage of 50 mg/kg/day and MIR at a dosage of 30 mg/kg/day. The treatment duration was 35 days. Sperm samples were collected from the caudal region of the epididymis post-euthanasia to assess the total mean sperm count, sperm viability, motility, DNA damage, and morphology. Testicular tissue was employed to quantify total antioxidant capacity (TAC), superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) concentrations, while serum levels of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were analyzed. Additionally, various aspects, including testicular histopathology, oxidative enzyme levels, gene expression related to apoptosis and antiapoptotic pathways, and in vivo fertility index, were evaluated after 35 days. The QUE, MIR, and QUE + MIR groups showed less abnormal morphology and DNA damage, as well as better total and progressive sperm motility, motility characteristics, viability, and plasma membrane function compared to the PHZ group. QUE, MIR, and QUE + MIR administration increased TAC, SOD, and GPx activities in testicular tissue, while reducing MDA levels compared to the PHZ group. Furthermore, QUE, MIR, and QUE + MIR significantly reduced Bax, and caspase-3 expression levels, and increased Bcl-2 expression levels, compared to the PHZ group. Mice treated with QUE, MIR, and QUE + MIR exhibited an increased in vivo fertility index and plasma sex hormone levels compared to the PHZ group. These results show that QUE, MIR, and QUE + MIR might be able to improve the fertility index, boost the testicular antioxidant defense system, and control the death of germ cells. This could mean that they could be used to treat mice with PHZ-induced testicular damage.

The Effects of Ferulic Acid, Tryptophan, and L-Glutamine on the Cryopreservation of Mouse Spermatozoa

In this study, the effects of ferulic acid (0.1, 1, ve 10 mM), tryptophan (5, 25, ve 50 mM), and L-glutamine (10, 50, ve 100 mM) at different doses added to 18% raffinose + 3% skimmed milk powder sperm extender on the freezing of mouse spermatozoa in liquid nitrogen were investigated. The combination of 18% raffinose + 3% skimmed milk powder without additives was used as the control group. Frozen spermatozoa were thawed in a 37°C water bath for 30 seconds. After freeze-thawing, motility, dead spermatozoa ratio, plasma membrane integrity, abnormal acrosome ratio, motility endurance (for 4 hours), and cell apoptosis tests were performed in Human Tubal Fluid (HTF). Compared with the control group after freezing and thawing, the highest motility and plasma membrane integrity were obtained in the 10 mM L-glutamine group with 56.6% ± 2.11% and 77.8% ± 0.87%, respectively (p < 0.05). In addition, when compared to the control group, the lowest rate of dead spermatozoa and abnormal acrosome was found in the 10 mM L-glutamine group as 26.0% ± 1.46% and 6.3% ± 1.09%, respectively (p < 0.05). The highest motility values for spermatozoa endurance were determined in the 10 and 50 mM L-glutamine groups up to the 4th hour compared to the control group (p < 0.05). In the evaluation of apoptosis in semen samples, there was no significant difference between the control, 0.1 mM ferulic acid, and 10 mM L-glutamine groups (p > 0.05). As a result, it was determined that the addition of 10 mM L-glutamine to the spermatozoa extender increased the motility, viable spermatozoa, functional membrane integrity, intact acrosome ratios, or motility endurance after freeze-thawing and could be used successfully in the freezing extender of mouse spermatozoa.

Recovering Spermatogenesis By Protected Cryopreservation Using Metformin and Transplanting Spermatogonial Stem Cells Into Testis in an Azoospermia Mouse Model

Cryopreservation and transplantation of spermatogonial stem cells (SSCs) may serve as a new method to restore male fertility in patients undergoing chemotherapy or radiotherapy. However, SSCs may be damaged during cryopreservation due to the production of reactive oxygen species (ROS). Therefore, different antioxidants have been used as protective agents. Studies have shown that metformin (MET) has antioxidant activity. The aim of this study was to assess the antioxidant and antiapoptotic effects of MET in frozen-thawed SSCs. In addition, the effect of MET on the proliferation and differentiation of SSCs was evaluated. To this end, SSCs were isolated from mouse pups aged 3-6 days old, cultured, identified by flow cytometry (ID4, INTEGRIN β1+), and finally evaluated for survival and ROS rate. SSCs were transplanted after busulfan and cadmium treatment. Cryopreserved SSCs with and without MET were transplanted after 1 month of cryopreservation. Eight weeks after transplantation, the recipient testes were evaluated for the expression of apoptosis (BAX, BCL2), proliferation (PLZF), and differentiation (SCP3, TP1, TP2, PRM1) markers using immunohistochemistry, Western blot, and quantitative real-time polymerase chain reaction. The findings revealed that the survival rate of SSCs was higher in the 500 μm/mL MET group compared to the other groups (50 and 5000 μm/mL). MET significantly decreased the intracellular ROS production. Transplantation of SSCs increased the expression level of proliferation (PLZF) and differentiation (SCP3, TP1, TP2, PRM1) markers compared to azoospermia group, and their levels were significantly higher in the MET group compared to the cryopreservation group containing basic freezing medium (p < 0.05). MET increased the survival rate of SSCs, proliferation, and differentiation and decreased the ROS production and the apoptosis rate. Cryopreservation by MET seems to be effective in treating infertility.

Is glycerol a good cryoprotectant for sperm cells? New exploration of its toxicity using avian model

Glycerol is a cryoprotectant used widely for the cryopreservation of animal sperm, but it is linked to a decrease in fertility. The mechanism underlying the negative effects of glycerol remains unclear. Therefore, in this study, we aimed to gain a better understanding by using the chicken model. First, we investigated the impact of increasing the concentration of glycerol during insemination on hen fertility. Our findings revealed that 2% glycerol resulted in partial infertility, while 6% glycerol led to complete infertility. Subsequently, we examined the ability of sperm to colonize sperm storage tubules (SST) during in vivo insemination and in vitro incubation. The sperm used in the experiment were stained with Hoechst and contained 0, 2, or 6% glycerol. Furthermore, we conducted perivitelline membrane lysis tests and investigated sperm motility, mitochondrial function, ATP concentration, membrane integrity, and apoptosis after 60 min of incubation with different glycerol concentrations (0%, 1%, 2%, 6%, and 11%) at two temperatures to simulate pre-freezing (4 °C) and post-insemination (41 °C) conditions. Whereas 2% glycerol significantly reduced 50% of sperm containing SST, 6% glycerol completely inhibited SST colonization in vivo. On the other hand, in vitro incubation of sperm with SST revealed no effect of 2% glycerol, and 6% glycerol showed only a 17% reduction in sperm-filled SST. Moreover, glycerol reduced sperm-egg penetration rates and also affected sperm motility, bioenergetic metabolism, and cell death at 4 °C. These effects were observed when the concentration of glycerol exceeded 6%. Furthermore, at 41 °C, glycerol caused even greater damage, particularly in terms of reducing sperm motility. These data altogether reveal important effects of glycerol on sperm biology, sperm migration, SST colonization, and oocyte penetration. This suggests that glycerol plays a role in reducing fertility and presents opportunities for improving sperm cryopreservation.

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 Ascorbic Acid and Proline Amino Acid Supplementations on Cryosurvival and Fertility Rates of Cryopreserved Honey Bee (Apis mellifera) Semen

This study investigated the effect of ascorbic acid (vitamin C) and proline amino acid alone or together on the quality and fertility of frozen/thawed honey bee spermatozoa. The experiments were designed to compare a single ascorbic acid, a single proline amino acid, and different combinations of ascorbic acid with proline amino acid on the cryopreservation of honey bee semen based on sperm motility, viability, intact membrane (hypo-osmotic swelling test), and fertility rates. Eight cryopreserved study groups comprised Control II with no supplement, along with groups with ascorbic acid (2 mg), proline 25 mM, proline 50 mM, proline 100 mM, and combination groups of both ascorbic acid (2 mg) and proline 25 mM, proline 50 mM, and lastly proline 100 mM groups, respectively. Using 50 mM proline in the tested groups had the greatest impact on sperm motility, viability, the percentage of spermatozoa with intact membrane, and fertility. The cryopreservation process caused a gradual decrease in motility, viability, intact membrane (p < 0.05), and fertility rates (p < 0.01) in all the tested research groups as against the fresh semen control group. Successful honey bee sperm cryopreservation and fertility are achievable when using an appropriate sperm freezing protocol and antioxidant. Proline amino acid as an antioxidant in semen extender had a more beneficial influence on sperm quality parameters and fertility. The success of cryopreservation with antioxidants is related to the chosen antioxidant in a dose-dependent manner.

A triple stain method in conjunction with an in-depth screening of cryopreservation effects on post-thaw sperm in dogs

In order to accurately analyze the possible side effects of sperm cryopreservation, an in-depth screening of post-thaw sperm status is necessary. Thus, this study aimed to identify thorough effects of sperm cryopreservation, by evaluating the integrity of all specific structures of the canine spermatozoa. Thirteen (n = 13) mature dogs of different breeds were selected. Six dogs (n = 6) were subjected to sperm cryopreservation, whereas seven dogs (n = 7) were used as semen donors to validate a simultaneous assessment of sperm plasmatic, acrosomal, and mitochondrial membranes (triple stain) by fluorescent probes. Fresh and post-thaw semen samples were evaluated through a computer-assisted analysis of sperm motility, sperm morpho-functional evaluation, triple stain and sperm DNA integrity. Post-thaw semen samples had lower total and progressive motility, as well as higher percentage of minor and major defects. Moreover, post-thaw samples had higher percentage of sperm with plasma membrane and mitochondrial damage but intact acrosome, and also sperm with simultaneous damaged plasma, acrosomal and mitochondrial membranes. Furthermore, post-thaw sperm had higher protamination deficiency and DNA fragmentation. In conclusion, cryopreservation has a broad impact in sperm morphology and function, altering motility patterns, plasma, acrosome and mitochondrial membranes integrity, as well as sperm DNA.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section II

Simple Summary

In order to improve fertilization and pregnancy rates within artificial insemination or in vitro fertilization techniques in horses, producers may choose to select the best sperm within an ejaculate. In this paper, we review conventional and novel methods of sperm selection.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of available semen selection techniques. This segment of our two-section review will focus on the selection of spermatozoa based on quality and sex for equine intracytoplasmic sperm injection (ICSI), as well as current and future developments in sperm sorting technologies. Ultimately, novel methods of semen selection will be assessed based on their efficacy in other species and their relevance and future application towards ARTs in the horse.

Sperm Oxidative Stress during In Vitro Manipulation and Its Effects on Sperm Function and Embryo Development

Reactive oxygen species (ROS) generated at low levels during mitochondrial respiration have key roles in several signaling pathways. Oxidative stress (OS) arises when the generation of ROS exceeds the cell's antioxidant scavenging ability and leads to cell damage. Physiological ROS production in spermatozoa regulates essential functional characteristics such as motility, capacitation, acrosome reaction, hyperactivation, and sperm-oocyte fusion. OS can have detrimental effects on sperm function through lipid peroxidation, protein damage, and DNA strand breakage, which can eventually affect the fertility of an individual. Substantial evidence in the literature indicates that spermatozoa experiencing OS during in vitro manipulation procedures in human- and animal-assisted reproduction are increasingly associated with iatrogenic ROS production and eventual impairment of sperm function. Although a direct association between sperm OS and human assisted reproductive techniques (ART) outcomes after in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) is still a matter of debate, studies in animal models provide enough evidence on the adverse effects of sperm OS in vitro and defective fertilization and embryo development. This review summarized the literature on sperm OS in vitro, its effects on functional ability and embryo development, and the approaches that have been proposed to reduce iatrogenic sperm damage and altered embryonic development.

Carboxylated Poly-l-Lysine as a Macromolecular Cryoprotective Agent Enables the Development of Defined and Xeno-Free Human Sperm Cryopreservation Reagents

In human sperm cryopreservation, test yolk buffer and human serum albumin have been used as permeating macromolecular-weight cryoprotectants. In clinical reproductive medicine, human serum albumin is frequently used because of low risks of zoonoses and allergic reactions. However, the risk of allogeneic infectious diseases exists, and the supply may be unstable because human serum albumin is derived from human blood. Therefore, the development of xeno-free human sperm cryopreservative reagents that could overcome the aforementioned problems is warranted. We succeeded in developing a new xeno-free and defined sperm cryopreservation reagent containing glycerol, carboxylated poly-l-lysine, and raffinose. The cryopreservation reagent was not significantly different in terms of sperm motility, viability, and DNA fragmentation and was comparable in performance to a commercial cryopreservation reagent containing human serum albumin. Moreover, the addition of saccharides was essential for its long-term storage. These results may help elucidate the unknown function of macromolecular-weight permeating cryoprotective agents.

Green tea extract increases the quality and reduced DNA mutation of post-thawed Kacang buck sperm

The study aimed to determine the addition of green tea extract (GTE) in extender on the quality and DNA mutation of post-thawed Kacang buck sperm. The sperm DNA mutation was observed on nicotinamide adenine dinucleotide hydride (NADH) dehydrogenase 1 (ND1) of mitochondrial Deoxyribonucleic Acid (mtDNA). A pool of 12 Kacang buck ejaculates was diluted in skim milk-egg yolk extender contained 0, 0.05, 0.10, and 0.15 mg of GTE/100 mL for T0, T1, T2, and T3 group, respectively. Each of the aliquot groups was packaged in 0.25 mL French mini straw contained 60 million alive sperm and froze according to the protocol. The ND1 mtDNA amplification of samples was carried out Polymerase Chain Reaction machine, followed by DNA sequencing using the Sanger method. Meanwhile, the phylogenetic tree was constructed using the neighbor-joining (NJ) method with MEGA 7.0 software. The results showed that the T2 group maintained the highest quality for Kacang buck post-thawed semen. There was the highest percentages of sperms viability, motility, intact plasma membrane (IPM), the lowest of malondialdehyde (MDA) concentration, sperm DNA fragmentation (SDF), the total and types of ND1 mtDNA mutation frequency. The phylogenetic tree analysis revealed that the clade of the T2 group was most closely related to the sequence reference. However, there was no correlation between the semen quality parameters (sperm viability, motility, IPM, MDA concentration, and SDF) with ND1 mtDNA mutation of post-thawed Kacang buck semen. It could be concluded that GTE was useful as an antioxidant for Kacang buck semen extender for frozen sperm.

In vivo evaluation of the toxicity, genotoxicity, histopathological, and anti-inflammatory effects of the purified bioglycerol byproduct in biodiesel industry

BACKGROUND

Biodiesel has gained an increased popularity as a good alternative for fossil fuel because of its unusual qualities as a biodegradable, nontoxic, and renewable diesel fuel. Hence, the economic utilization of the accumulated bioglycerol byproduct became critically important for the sustainability of biodiesel industry. The purified bioglycerol might be used as a valuable industrial stock in cosmetic, medical, and food industries. However, if the purified product is going to be used in food, drug, or any industry that involves its ingestion or skin contact by human or animals, the product should be thoroughly tested on animal models.

RESULTS

The present study investigated the acute toxicity, anti-inflammatory, histopathological, and genotoxic effects of zeolite-purified biogylcerol on different animal models. All the previous tests proved the ability of the purification process to improve the qualities of the crude bioglycerol to a degree comparable to the pharmaceutical grade glycerol.

CONCLUSION

In other words, it could be concluded that zeolite-purified bioglycerol can be used in different industries that involves products consumed by human or animals.

Impact on using cryopreservation of testicular or epididymal sperm upon intracytoplasmic sperm injection outcome in men with obstructive azoospermia: a systematic review and meta-analysis

PURPOSE

To determine whether there was a significant impact on using cryopreservation of testicular or epididymal sperm upon the outcomes of intracytoplasmic sperm injection (ICSI) in patients with obstructive azoospermia (OA).

METHOD

Systematic review and meta-analysis of 20 retrospective studies in databases from January 1, 1995, to June 1, 2020.

RESULT

Twenty articles were included in this study. A total of 3602 (64.1%) of 5616 oocytes injected with fresh epididymal sperm were fertilized, compared with 2366 (61.2%) of 3862 oocytes injected with cryopreserved sperm (relative risk ratio (RR) 0.96, 95% confidence interval (CI) (0.90, 1.02), P > 0.05). A total of 303 (44.1%) of 687 ICSI cycles using fresh epididymal sperm resulted in a clinical pregnancy, compared with 150 (36.6%) of 410 ICSI cycles using cryopreserved epididymal sperm (RR 0.84, 95% CI (0.72, 0.97), P < 0.05). In the testis, a total of 2147 (68.7%) of 3125 oocytes injected with fresh sperm were fertilized, compared with 1623 (63.5%) of 2557 oocytes injected with cryopreserved sperm (RR 0.97, 95% CI (0.90, 1.06), P > 0.05). A total of 151 (47.8%) of 316 ICSI cycles using fresh testicular sperm resulted in a clinical pregnancy, compared with 113 (38.2%) of 296 ICSI cycles using cryopreserved sperm (RR 0.87, 95% CI (0.72, 1.05), P > 0.05).

CONCLUSIONS

In men with OA, there was a statistical lower clinical pregnancy rate (CPR) by using frozen epididymal sperm compared with fresh epididymal sperm, but showing no difference on fertilization rate (FR). Additionally, FR and CPR were not affected by whether the retrieved testicular sperm was frozen or fresh.

Acrosome and chromatin integrity, oxidative stress, and expression of apoptosis-related genes in cryopreserved mouse epididymal spermatozoa treated with L-Carnitine

Oxidative stress is believed to be an important cause of sperm damage during freezing. l-Carnitine (LC) may have the potential to improve sperm quality after frozen-thawed process. The present study aimed to investigate the effect of LC supplementation in cryoprotectant media of mouse epididymal sperm on post-thaw sperm quality and expression of apoptosis-related genes. Male BALB/cJ mice spermatozoa were cryopreserved in a cryoprotectant medium containing 2.5 or 5 mM LC. The untreated group was cryopreserved with the cryoprotectant medium only. Six months following cryopreservation, the samples were thawed and sperm quality parameters, chromatin and acrosome integrity, reactive oxygen species (ROS) and glutathione (GSH) levels, mitochondrial activity, and mRNA expression of Bax and Bcl-2 were assessed. The results demonstrated that the concentration of 5 mM LC in cryoprotectant media exhibited higher values for the sperm quality parameters and integrity of chromatin and acrosome in post-thaw spermatozoa than those of the untreated group. Furthermore, sperm ROS levels decreased while GSH and mitochondrial activity levels increased in 5 mM LC group compared to those in the untreated group (P < 0.01). In 5 mM LC-treated group, Bax was down-regulated (P < 0.05) while Bcl-2 was up-regulated (P < 0.001) compared to the untreated group. Collectively, LC supplementation of cryoprotectant medium improved the quality of frozen-thawed mouse epididymal spermatozoa, as showed reduced ROS level and Bax expression as well as increased GSH, mitochondrial activity, and Bcl-2 expression.

DNA fragmentation index (DFI) as a measure of sperm quality and fertility in mice

Although thousands of genetically modified mouse strains have been cryopreserved by sperm freezing, the likelihood of cryorecovery success cannot be accurately predicted using conventional sperm parameters. The objective of the present study was to assess the extent to which measurement of a sperm DNA fragmentation index (DFI) can predict sperm quality and fertility after cryopreservation. Using a modified TUNEL assay, we measured and correlated the DFI of frozen-thawed sperm from 83 unique mutant mouse strains with sperm count, motility and morphology. We observed a linear inverse correlation between sperm DFI and sperm morphology and motility. Further, sperm DFI was significantly higher from males with low sperm counts compared to males with normal sperm counts (P < 0.0001). Additionally, we found that viable embryos derived using sperm from males with high DFI (62.7 ± 7.2% for IVF and 73.3 ± 8.1% for ICSI) failed to litter after embryo transfer compared to embryos from males with low DFI (20.4 ± 7.9% for IVF and 28.1 ± 10.7 for ICSI). This study reveals that measurement of DFI provides a simple, informative and reliable measure of sperm quality and can accurately predict male mouse fertility.

Improved Post-Thaw Quality of Canine Semen after Treatment with Exosomes from Conditioned Medium of Adipose-Derived Mesenchymal Stem Cells

Freezing decreases sperm quality, ultimately affecting fertilizing ability. The repair of freeze-damaged sperm is considered crucial for improving post-thaw viability and fertility. We investigated the effects of exosomes derived from canine adipose-derived mesenchymal stem cells on dog sperm structure and function during cryopreservation. The pooled ejaculate was diluted with buffer, without (Control), or with exosomal proteins (25, 50, or 100 µg/mL). Using fresh semen, the determined optimal exosomal protein concentration was 50 µg/mL (Group 2) which was used in further experiments. Post-thaw sperm treated with exosomes were superior to control (p < 0.05) in terms of motility (56.8 ± 0.3% vs. 47.2 ± 0.3%), live sperm percentage (55.9 ± 0.4% vs. 45.4 ± 0.4%), membrane integrity (55.6 ± 0.5% vs. 47.8 ± 0.3%), and acrosome integrity (60.4 ± 1.1% vs. 48.6 ± 0.4%). Moreover, expression of genes related to the repair of the plasma membrane (ANX 1, FN 1, and DYSF), and chromatin material (H3, and HMGB 1) was statistically higher in exosome-treated sperm than control, but the expression of the mitochondrial reactive oxygen species modulator 1 gene was significantly higher in control. Therefore, exosomal treatment may improve the quality of post-thaw dog semen through initiating damaged sperm repair and decreasing reactive oxygen species production.

Comparative analysis between slow freezing and ultra-rapid freezing for human sperm cryopreservation

Objective

Cryopreservation of human spermatozoa is fundamental in assisted reproductive technology. At present, slow freezing techniques are widely used for sperm cryopreservation. Recently, sperm vitrification has been proposed as an alternative to slow freezing. This study aimed to compare the efficiency of slow versus ultra-rapid freezing after thawing and to determine the level of DNA fragmentation in post-thaw normal human semen samples processed through each of the cryopreservation techniques.

Methods

Ultra-rapid freezing is a method that only differs from conventional ultra-rapid freezing in the use of sucrose as a cryoprotectant. In experiment 1, 24 semen samples were used to compare sperm recovery rates after slow and ultra-rapid sperm freezing. In experiment 2, 18 semen samples were used to compare post-thaw sperm DNA fragmentation levels after each of the cryopreservation techniques.

Results

In experiment 1, no significant differences were observed in sperm concentration recovery rates, although slow freezing showed a lower progressive motility rate than ultra-rapid freezing (16.6±7.4% vs. 34.7±10.2%), and higher non-progressive and immotile sperm counts (9.0±4.0% vs. 7.6±2.8%; and 74.4±10.1% vs. 57.8±10.3%, respectively). In experiment 2, sperm DNA fragmentation after thawing was significantly higher in slow freezing than in fresh post gradient processing and ultra-rapid freezing samples (47.3±13.4% vs. 9.1±3.7% vs. 14.6±4.6%, respectively).

Conclusion

Sperm ultra-rapid freezing may be an alternative to slow freezing with better recovery results and less apparent DNA damage.

Effects of human sperm cryopreservation on apoptotic markers in normozoospermic and non-normozoospermic patients

SummaryThe negative effects of cryopreservation on sperm parameters are well documented but little information is known about molecular basis of the process. The aim of the present study was to investigate the possible effects of sperm cryopreservation on main apoptotic signs including DNA fragmentation and caspase-3 activation and to determine if these effects vary according to sperm parameters. Sperm samples of 72 patients were cryopreserved. The patients were sub-grouped as normozoospermic or non-normozoospermic patients according to their semen parameters. DNA fragmentation rates and caspase-3 activation levels were analyzed before and after cryopreservation in both groups. Mean DNA fragmentation rate was increased significantly from 23.98% in neat semen samples to 27.34% after cryopreservation (P = 0.03). DNA fragmentation rates were slightly higher in non-normozoospermic patients compared with the normozoospermic patients in both the neat semen and after cryopreservation (23.25 and 24.71% vs. 26.32 and 28.36%, respectively) although the difference obtained were not statistically significant. An increasing trend for caspase-3 activations (0.093 vs. 0.116) was observed after cryopreservation but the differences were not statistically significant. Caspase-3 activation was found to be slightly higher in non-normozoospermic patients both in the neat semen and after cryopreservation compared with the normozoospermic patients but the differences were not statistically significant. Caspase-3 expression was also shown using immunocytochemistry in both fresh ejaculated sperm and thawed sperm after cryopreservation but at different localizations. The cryopreservation process had detrimental effects on sperm quality but the quality of the sperm samples was not adversely effective for the apoptotic markers including DNA fragmentation and caspase-3 activation patterns. In fact, it was the cryopreservation process itself that adversely effected the above apoptotic markers and apoptosis. It was concluded therefore that sperm cell cryopreservation triggers apoptosis after thawing and this process adversely affects semen parameters.

Gamete cryopreservation of Australian 'old endemic' rodents – spermatozoa from the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis)

Most of the Australian ‘old endemic’ rodents have greatly reduced distributions with several species now threatened with extinction. Application of assisted reproductive technology has the potential to assist in their conservation programs in at least a few species. Here we describe an attempt to cryopreserve spermatozoa from two of these species – those of the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis), which have dramatic differences in sperm morphology. Slow and rapid freezing and three different cryoprotectant media with either raffinose, glycerol and/or skim milk were used and the results compared with those of house mouse sperm, which were used as controls. Sperm morphology, motility, membrane integrity and DNA damage were determined. Prior to cryopreservation there was a higher percentage of morphologically normal, motile, P. australis sperm than in those from N. alexis. Following cryopreservation, regardless of treatment, the percentage of motile sperm was low but it was higher when raffinose with skim milk was used as a cryoprotectant than in raffinose with glycerol albeit that minimal differences in membrane integrity or DNA damage were evident. Raffinose with skim milk should thus be used as a cryoprotectant for storing sperm of these Australian rodents in the future.

Gradient sperm selection for reproductive techniques in cattle: Is Isolate a suitable replacement for Percoll?

In assisted reproductive techniques, it is essential to perform a sperm selection to obtain spermatozoa with high motility and membrane integrity for in vitro fertilisation (IVF) and high-DNA integrity for intracytoplasmic sperm injection (ICSI). In this study, we evaluated whether Isolate^® was a suitable substitute for Percoll^® for assisted reproductive techniques. Commercial cryopreserved bovine semen was used after selection in both gradients, and plasma and acrosome membrane integrity, reactive oxygen species (ROS) levels, DNA integrity and mitochondrial membrane potential (ΔΨm) were assessed by flow cytometry. Motility parameters were also evaluated by CASA system. A similar percentage of spermatozoa with intact plasma membrane, acrosome integrity and high ΔΨm was observed in both sperm selection methods, but only Percoll^® showed higher percentage of spermatozoa with intact plasma and acrosome membrane compared to the post-thawing group. No differences were observed in the motility, ROS, DNA fragmentation and on the in vitro embryo production in all experimental groups. In conclusion, the selection of bovine spermatozoa with Isolate^® generates spermatozoa with similar quality parameters and embryonic development compared to Percoll^® providing a suitable alternative sperm selection method for assisted reproductive techniques in this species.

Consequences of adding gum Arabic as a cryoprotectant on motility and viability of frozen stallion semen

A trial was conducted to check effect of adding gum Arabic (GA) instead of egg yolk (EY) as a cryoprotectant for stallion sperm. Two experiments were designed; experiment I tested adding 3 levels of nonheated GA (i.e., 3, 6 and 9 g/100 mL diluents) in HF-20 extender. However, in experiment II the same levels were tested except that GA was heated at 80 °C for 60 min. HF-20 containing 10% of EY was used as control. In experiment I, sperm frozen in HF-20 containing nonheated GA exhibited lower percentages of motile sperm, progressively motile sperm and sperm with intact plasma membranes, vitality rate, and acrosome integrity after cooling or after deep freezing. Frozen semen in HF-20 containing 3-6% of preheated GA in experiment II maintained sperm motility at 46-50% and elevated progressive motility at 27%. The semen diluted in preheated GA (6%) and frozen exhibited a fertility rate of 40% (2/5). A similar fertility rate (40%) was found in the control semen (i.e. 10%) compared to those that were inseminated with frozen semen in preheated 3% GA (20%, 1/5). These results suggest that preheated GA could be used as an alternative cryoprotectant for cryopreserving stallion sperm.

Comparative study of fertilization rates of C57BL/6NKorl and C57BL/6N mice obtained from two other sources

C57BL/6N is the most widely used inbred mouse strain applied in a wide variety of research areas including cancer, cardiovascular biology, developmental biology, diabetes and obesity, genetics, immunology, neurobiology, and sensorineural research. To compare the fertilization rates of C57BL/6NKorl mice with two commercial C57BL/6N stocks, differences in reproductive organ structures, sperm and egg numbers, fertilization rates, and embryo development rates among C57BL/6NKorl (Korea FDA source), C57BL/6NA (USA source), and C57BL/6NB (Japan source) mice were determined. Among the stocks, no significant differences were detected in organ weight and histological structure of male and female reproductive organs, although body weight was higher in C57BL/6NKorl mice than that in the other groups. The concentration and morphology of sperm and eggs in C57BL/6NKorl mice were similar to those of C57BL/6NA and C57BL/6NB mice. Furthermore, the three stocks had similar in vitro fertilization and embryo development rates, although these rates tended to be higher in C57BL/6NB mice. Pup body weight was higher in C57BL/6NKorl and C57BL/6NB mice than that in C57BL/6NA mice. The results of the present study suggest that C57BL/6NKorl, C57BL/6NA, and C57BL/6NB mice obtained from three different sources have similar fertilization and embryo development rates, although there were slight differences in the magnitude of their responses rates.

Cryopreservation of Nili-Ravi buffalo (Bubalus bubalis) semen in AndroMed® extender; in vitro and in vivo evaluation

The study was designed to evaluate AndroMed^® for the freezability and fertility of Nili-Ravi buffalo semen. Semen was collected from four adult Nili-Ravi buffalo (Bubalus bubalis) bulls for 3 weeks (replicate). Semen ejaculates from each buffalo bull were divided into three aliquots. One aliquot was used for evaluation of motility, plasma membrane integrity, livability, viability, DNA integrity and normal apical ridge. Remaining two aliquots were diluted (37°C; 50 × 10⁶ spermatozoa/ml) in tris-citric egg yolk or AndroMed^® extender and cryopreserved in 0.5 ml French straws. After thawing, per cent post-thaw motility (47.9 ± 0.8, 49.2 ± 1.7), plasma membrane integrity (44.4 ± 1.2, 46.8 ± 1.8) and normal apical ridge (81.4 ± 0.3, 83.2 ± 0.3) were recorded similar (p > .05) in tris-citric egg yolk and AndroMed^® extender. Higher (p < .05) percentage of sperm livability (70.5 ± 1.4 and 64.4 ± 1.0), viability (67.5 ± 1.5 and 61.5 ± 0.6) and DNA integrity (97.0 ± 0.3 and 93.4 ± 0.21) were recorded in AndroMed^® compared to tris-citric egg yolk post-thaw. Values for all the aforementioned spermatozoal quality parameters were observed lower (p < .05) in frozen-thawed compared to fresh semen irrespective of the experimental extenders. Fertility rates of buffalo semen did not differ (p > .05) either cryopreserved in tris-citric egg yolk or AndroMed^® extender (45.5% vs. 49%). It is concluded that AndroMed^® is capable in protecting the buffalo bull sperm during freeze-thawing process and can be adopted safely for routine use replacing the tris-citric egg yolk extender in artificial insemination programme.

Minimal volume vitrification of epididymal spermatozoa results in successful in vitro fertilization and embryo development in mice

This study compared three cryopreservation protocols on sperm functions, IVF outcomes, and embryo development. Epididymal spermatozoa cryopreserved using slow-cooling (18% w/v raffinose, RS-C) were compared with spermatozoa vitrified using 0.25 M sucrose (SV) or 18% w/v raffinose (RV). The motility, vitality, and DNA damage (TUNEL assay) of fresh control (FC) spermatozoa were compared with post-thawed or warmed RS-C, RV, and SV samples. Mouse oocytes (n = 267) were randomly assigned into three groups for insemination: RV (n = 102), RS-C (n = 86), and FC (n = 79). The number and the proportion of two-cell embryos and blastocysts from each treatment were assessed. Sperm motility (P < 0.01) and vitality (P < 0.05) were significantly reduced after vitrification compared with slow-cooled spermatozoa. However, DNA fragmentation was significantly reduced in spermatozoa vitrified using sucrose (15 ± 1.8% [SV] vs 26 ± 2.8% [RV] and 27 ± 1.2% [RS-C]; P < 0.01). Although the number of two-cell embryos produced by RS-C, RV, and FC spermatozoa was not significantly different, the number of blastocysts produced from two-cell embryos using RV spermatozoa was significantly higher than FC spermatozoa (P = 0.0053). This simple, small volume vitrification protocol and standard insemination method allows successful embryo production from small numbers of epididymal spermatozoa and may be applied clinically to circumvent the need for ICSI, which has the disadvantage of bypassing sperm selection.

In vitro fertilization with cryopreserved spermatozoa in small pieces of gonad of the scallop Argopecten purpuratus (Lamarck, 1819)

The aim of this work was to evaluate the fertilization rates through the first cleavage, obtained with fresh oocytes inseminated with sperm cryopreserved at different freezing rates (-8.8,-10 and -12 °C/min) and at two thawing rates, using cryoprotectant solution (Me2SO, at 1 M, 2 M, 3 M, 4 M and 5 M with or without egg yolk and sucrose). Sperm contained in small pieces of male gonad were frozen at the three freezing rates, stored in liquid nitrogen and later the samples were thawed at two rates by immersing the samples in water at 50 °C (rapid) or 30 °C. Control fertilization rates ranged from 69.2 ± 2.8%-45.5% ± 1.6%. To determine the best concentration of the cryoprotectant (between 1 M and 5 M), in a first step, a freezing of -15 °C/min and a rapid thawing was used. Fertilization rates ranged between 9.6 ± 2.5% and 34.6± 12.2% and the highest percentages of fertilized oocytes (34.6%) was obtained with 3 M concentration with cryoaditive. The second step, using 3 M Me2SO with cryoadditive, determined that the freezing rate -8.8 °C/min produces the best result 29 ± 2.9% of fertilized oocytes corresponding to 59.2 ± 9.1% compared to controls. Although there were no significant differences among the different freezing rates, the fertilization rate tended to be higher with a lower freezing rate. Comparing the results of the present study, which used a cryoprotective solution composed of Me2SO and a cryoadditive, to those of other studies that used Me2SO without cryoadditives, suggests that the addition of a cryoadditive to the cryoprotectant Me2SO improves the fertilizing capacity of the sperm of Argopecten purpuratus after being cryopreserved.

Effect of nerve growth factor on sperm quality in asthenozoosprmic men during cryopreservation

BACKGROUND

Although routinely used in assisted reproductive technology, human sperm cryopreservation is not an entirely successful procedure. This study determined the effect of nerve growth factor (NGF) supplementation of cryopreservation medium on post-thaw viability, motility, intracellular nitric oxide (NO) concentration, and DNA fragmentation of human spermatozoa in asthenozoospermic men.

METHODS

Semen samples were collected from 25 asthenozoosprmic men and divided into the following groups (n = 5/group): fresh semen (control); frozen-thawed semen without treatment; frozen-thawed semen with NGF treatment (0.5, 1, and 5 ng/ml). Prior to dividing the asthenozoospermic samples, 200 μl of each sample was collected for NGF content assessment by ELISA and then compared with normozoospermic semen samples (25 normozoospermic men). Sperm motility and viability were assessed according to WHO criteria. Furthermore, intracellular nitric oxide and DNA fragmentation were evaluated by Flow Cytometry.

RESULTS

NGF content was significantly higher in normozoospermic compared with asthenozoospermic men. Cryopreservation of asthenozoospermic semen samples significantly decreased sperm viability and motility, and increased intracellular nitric oxide concentration and DNA damage (p < 0.01). In asthenozoospermic frozen-thawed samples treated with 0.5 ng/ml exogenous NGF, we observed a significantly increased viability, motility, and decreased DNA fragmentation (p < 0.05), but intracellular nitric oxide concentration was not reduced. The other high doses (1 and 5 ng/ml) had no significant effect on the variables.

CONCLUSION

Supplementation with exogenous NGF could have partial and limited protective effect during cryopreservation of human spermatozoa but further research is needed to evaluate the possible clinical applications.

Effect of cholesterol-loaded cyclodextrin on cryosurvival and fertility of cryopreserved carp (Cyprinus carpio) sperm

Addition of cholesterol-loaded cyclodextrin (CLC) to the diluents of mammalian semen increased stability and rigidity of phospholipid hydrocarbon chains of plasma membrane during sperm cryopreservation process. CLC has been tested successfully as cryoprotectant in various livestock sperm cryopreservation protocols but its efficacy for cryopreserving of fish sperm has not previously been tested. In the present study, different cholesterol loaded cyclodextrin concentrations were evaluated for the cryopreservation of carp (Cyprinus carpio) sperm. Sexually mature fish were induced to spermiation and ovulation with Ovopel. The extenders were prepared by using 300 mM glucose and 10% DMSO supplemented with different concentrations of CLC (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0mg per 120×10(6) spermatozoa) and without CLC (control). The pooled semen was diluted separately at a ratio of 1:3 (v/v) by using CLC extenders. Diluted semen placed into 0.25 ml straws were equilibrated at 4°C for 15 min and frozen in liquid nitrogen vapor. Fertilization was conducted using a ratio of 1×10(5) spermatozoa/egg. Fresh sperm with no treatment showed the greatest sperm motility, duration of motility, viability, and fertilization results compared to the other tested cryopreserved and control groups (p<0.05). Supplementation of 1.5 mg CLC to the extender showed the best cryoprotective effect for sperm motility, duration of motility, and viability against freezing damage in comparison to extenders containing 2.5 mg, 3.0 mg CLC, and control group (p<0.05). Cryopreserved sperm containing 1.5 mg CLC provided greater result in term of fertilization success when compared to other extenders containing 0.5, 2.5, and 3.0 mg CLC or control (p<0.05). The amount of CLC effected post-thaw sperm quality and fertility as a dose-dependent manner. It is concluded that treatment of cholesterol-loaded cyclodextrin for carp sperm cryopreservation significantly improves cell cryosurvival and fertilization.

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.

Effect of metformin on the fertilizing ability of mouse spermatozoa

Numerous antioxidants have been added to cryopreservation media with varied success. The biguanide, metformin, commonly used for the treatment of type II diabetes, possesses properties impacting metabolism control that have not been yet assessed in cryopreservation protocols. The aim of this experiment was to; (i) determine the effect of metformin on fresh spermatozoa properties; and (ii) to assess positive or negative effects of metformin in post-thaw function and fertilizing capacity of mouse spermatozoa when used in cryopreservation media. The experiments have shown that the presence of metformin in fresh semen did not induce negative effects on spermatozoa quality, except a slight reduction in sperm motility at 5000μM metformin. However, when metformin was included in a cryopreservation protocol, an improvement in the fertilization rate and a reduction in the percentage of abnormal zygotes after in vitro fertilization was observed. In conclusion, metformin did not affect sperm quality at low concentrations (50μM), but its presence in the cryopreservation media could represent a benefit to improve the quality of frozen semen.

An evaluation of soybean lecithin as an alternative to avian egg yolk in the cryopreservation of fish sperm

Plant-derived lecithin has been used as a more sanitary alternative to avian egg yolk in livestock sperm cryopreservation protocols but its efficacy for cryopreserving fish sperm has not previously been tested comparatively. Here various concentrations of soybean lecithin were evaluated for the cryopreservation of carp (Cyprinus carpio) sperm. Sexually mature fish were induced to spermiation and ovulation with ovopel. The extenders were prepared by using 300 mM glucose, 10% DMSO, supplemented with different ratios of lecithin (5%, 10%, 15%, and 20%) and 10% egg yolk (control I). Negative control was made without egg yolk and soybean lecithin (control II). The pooled semen was diluted separately at ratio of 1:3 (v/v) by using egg yolk and soybean-based extenders. Diluted semen placed into 0.25 ml straws were equilibrated at 4 °C for 15 min and frozen in liquid nitrogen vapor. Fertilization was conducted using a ratio of 1 × 10(5)spermatozoa/egg. Supplementation of 10% lecithin to extender showed the best cryoprotective effect for sperm motility and duration of motility against freezing damage compared to 15%, 20% and control II groups (p<0.05). Cryopreserved sperm with extender containing 10% lecithin provided a greater result in terms of fertilization success when compared to extenders containing 20% lecithin or control II (p<0.05). It is concluded that the animal protein-free extender containing 10% soybean lecithin has a similar cryoprotective actions with conventional egg yolk-based extender against freezing damages and fertilization. Therefore, soybean lecithin is a suitable alternative to avian egg yolk for the cryopreservation of fish sperm.

Improved assessment of frozen/thawed mouse spermatozoa using fluorescence microscopy

Genetically modified (GM) animals are unique mutants with an enormous scientific potential. Cryopreservation of pre-implantation embryos or spermatozoa is a common approach for protecting these lines from being lost or to store them in a repository. A mutant line can be taken out of a breeding nucleus only if sufficient numbers of samples with an appropriate level of quality are cryopreserved. The quality of different donors within the same mouse line might be heterogeneous and the cryopreservation procedure might also be error-prone. However, only limited amounts of material are available for analysis. To improve the monitoring of frozen/thawed spermatozoa, commonly used in vitro fertilization (IVF) followed by embryo transfer were replaced with animal-free techniques. Major factors for assessing spermatozoa quality (i.e., density, viability, motility, and morphology) were evaluated by fluorescence microscopy. For this, a live/dead cell staining protocol requiring only small amounts of material was created. Membrane integrity was then examined as major parameter closely correlated with successful IVF. These complex analyses allow us to monitor frozen/thawed spermatozoa from GM mice using a relatively simple staining procedure. This approach leads to a reduction of animal experiments and contributes to the 3R principles (replacement, reduction and refinement of animal experiments).

Overview of new developments in and the future of cryopreservation in the laboratory mouse

The large-scale mutagenesis programmes underway around the world are generating thousands of novel GA mouse strains that need to be securely archived. In parallel with advances in mutagenesis, the procedures used to cryopreserve mouse stocks are being continually refined in order to keep pace with demand. Moreover, the construction of extensive research infrastructures for systematic phenotyping is fuelling demand for these novel strains of mice and new approaches to the distribution of frozen and unfrozen embryos and gametes are being developed in order to reduce the dependency on the transportation of live mice. This article highlights some contemporary techniques used to archive, rederive, and transport mouse strains around the world.