The effect of different concentrations of glycerol and DMSO on viability of Markhoz goat spermatozoa during different freezing temperatures steps

A brief review of the methodology and cryoprotectants in selected fish and mammalian species

Cryopreservation is a valuable technique used to assist in the genetic improvement of cultured stocks and provide a continuous supply of good-quality semen for artificial insemination. Conserving semen by cryopreservation serves several purposes (e.g. artificial reproductive technologies and species conservation) and is also used in the clinical treatment of human infertility. However, the lifespan of cryopreserved semen is influenced by a range of factors, including storage temperature, cooling rate, chemical composition of the extender, the concentration of cryoprotectant, reactive oxygen species, seminal plasma composition and hygienic control. The choice of cryoprotectant is a vital factor underlying the success of animal semen cryopreservation. In this regard, extensive research has been carried out on various cryoprotectants, such as egg yolk, dimethyl sulfoxide, methanol, ethylene glycol and dimethylacetamide. Recent studies have also described the use of a range of new cryoprotectants for cryopreservation, including compounds of plant origin (soy), amino acids, antifreeze proteins, carbohydrates and cyclodextrins. Moreover, semen cryopreservation and storage require the use of liquid nitrogen or ultralow refrigeration methods for both long- and short-term storage. This review summarizes the general methods used for freezing semen and discusses the use of traditional and newly emerging cryoprotectants (permeable and non-permeable) for the cryopreservation of semen in selected fish and mammalian species.

Effect of Some Plant-Based Substances on Microbial Content and Sperm Quality Parameters of Bull Semen

The rapid emergence of antibacterial resistance requires alternatives to antibiotics to be found, including for semen preservation. One of the possible alternatives would be to use plant-based substances with known antimicrobial effects. The objective of this study was to test the antimicrobial effect of pomegranate powder, ginger, and curcumin extract in two concentrations on bull semen microbiota after exposure for <2 h and 24 h. An additional aim was to evaluate the effect of these substances on sperm quality parameters. The bacterial count in semen was low from the beginning; however, a reduction was present for all tested substances compared with control. A reduction in bacterial count in control samples was also observed with time. Curcumin at a concentration of 5%, reduced bacterial count by 32% and was the only substance that had a slight positive effect on sperm kinematics. The other substances were associated with a decline in sperm kinematics and viability. Neither concentration of curcumin had a deleterious effect on sperm viability parameters measured by flow cytometry. The results of this study indicate that curcumin extract at a concentration of 5% can reduce the bacterial count and does not have a negative influence on bull sperm quality.

Inhibition of the cholesterol transporter ABCA1 by probucol decreases capacitation and tyrosine phosphorylation of dog spermatozoa, and is dose dependent

The ATP binding cassette (ABC) transporter molecule ABCA1 participates in the cholesterol transport within and through cell membranes. We recently demonstrated that in dog spermatozoa, capacitation could be decreased with probucol (PRO), an ABCA1 specific antagonist. In this study, a dose-effect relationship of PRO on dog sperm capacitation, tyrosine phosphorylation and cholesterol efflux from the sperm plasma membrane was investigated. A total of 16 ejaculates from dogs of different breeds, aged 2-4 years were used. Sperm motility and membrane integrity in the main fraction was determined by CASA. Samples were stained with a boron dipyrromethene difluoride (BODIPY) fluorophore (P9672, Sigma- Aldrich, A) diluted in DMSO at a final concentration of 0.4 μM. All samples were divided into 5 aliquots, with 0, 100, 250, 500 and 1000 μM of PRO. After incubation at 37 °C for 2 h, PI was added and flow cytometry performed. All aliquots were examined for capacitation and acrosome reaction by using the CTC assay and tyrosine phosphorylation (TP). Membrane integrity was measured in all aliquots to investigate the effect of PRO on cell membranes. Membrane integrity did not differ between controls (0 μM), and 100, 250 and 500 μM PRO, but decreased with 1000 μM PRO (p < 0.05). Increasing PRO concentration decreased the percentage alive cells with cholesterol efflux per PRO group (0 μM: 77.8 ± 10.6%, 100 μM: 63.7 ± 11.7%, 250 μM: 52.1 ± 12.9%, 500 μM: 37.7 ± 11.6%, 1000 μM: 33.1 ± 14.4%; p < 0.05), decreased head and entire tail phosphorylated cells (0 μM: 34.6%, 1000 μM: 5.1% p < 0.05); and decreased the percentage capacitated cells (maximum with PRO 500 μM: capacitated vs. control: 54.2 ± 17% vs 25 ± 7.7%, p < 0.05). Conclusion: PRO decreased the cholesterol efflux, and decreased tyrosine phosphorylation and capacitation in a dose-dependent manner. This suggests a strong involvement of the ABCA1 transporter in different functional aspects of sperm capacitation in dogs.

Influence of Two Widely Used Solvents, Ethanol and Dimethyl Sulfoxide, on Human Sperm Parameters

To study mechanisms involved in fertility, many experimental assays are conducted by incubating spermatozoa in the presence of molecules dissolved in solvents such as ethanol (EtOH) or dimethyl sulfoxide (DMSO). Although a vehicle control group is usually included in such studies, it does not allow to evaluate the intrinsic effect of the solvent on sperm parameters and its potential influence on the outcome of the experiment. In the present study, we incubated human spermatozoa for 4 h in a capacitation medium in the absence or the presence of different concentrations of EtOH and DMSO (0.1, 0.5, 1.0, and 2.0%) to assess the impact of these solvents on sperm motility, vitality, capacitation, and acrosome integrity. The presence of statistically significant relationships between increasing solvent concentrations and the investigated parameters was assessed using linear mixed models. A significant effect was observed with both solvents for total and progressive sperm motilities. We also evaluated the effect of time for these parameters and showed that the influence of the solvents was stable between 0 and 4 h, indicating an almost direct impact of the solvents. While EtOH did not influence sperm vitality and acrosome integrity, a significant effect of increasing DMSO concentrations was observed for these parameters. Finally, regarding capacitation, measured via phosphotyrosine content, although a dose-dependent effect was observed with both solvents, the statistical analysis did not allow to precisely evaluate the intensity of the effect. Based on the results obtained in the present study, and the corresponding linear mixed models, we calculated the concentration of both solvents which would result in a 5% decline in sperm parameters. For EtOH, these concentrations are 0.9, 0.7, and 0.3% for total motility, progressive motility, and capacitation, respectively, while for DMSO they are 1.5, 1.1, >2, 0.3 and >2% for total motility, progressive motility, vitality, capacitation, and acrosome integrity, respectively. We recommend using solvent concentrations below these values to dissolve molecules used to study sperm function in vitro, to limit side effects.

Dimethylformamide Preserves the Integrity of Cryopreserved Goat Semen in a Soybean Lecithin-Based Extender

This study investigated the cryoprotectant effects of dimethylformamide (DMF), ethylene glycol (EG), and dimethyl sulfoxide (DMSO) as substitutes for glycerol (GLY) in a soybean lecithin (SL)-based extender in the cryopreservation of buck sperm. In this study, the semen of three Saanen bucks was individually extended in SL supplemented with 5% GLY (control), DMF, EG, or DMSO. After this, the extended semen was cryopreserved and two straws from each group were thawed (37°C for 30 seconds), pooled, and analyzed for sperm motion parameters, plasma membrane integrity (PMI), acrosomal integrity (ACI), and high mitochondrial membrane potential (HMMP). Samples were analyzed after 15 minutes (T0) and after 2 hours of incubation at 37°C (T2). The results revealed higher values of motility (total and progressive) and sperm motion parameters for DMF than the other cryoprotectants (p < 0.0001). PMI and HMMP did not differ (p > 0.05) between GLY and DMF, but ACI was higher (p < 0.01) for DMF compared with GLY. Based on these results, DMF and GLY samples were used in heterologous in vitro fertilization assays by using bovine oocytes (n = 337) obtained from a slaughterhouse. No differences (p > 0.05) were observed between GLY and DMF for unfertilized (GLY: 38.8%; DMF: 25.33%), pronucleus (GLY: 25.68%; DMF: 27.92%), and cleavage rates (GLY: 35.52%; DMF: 46.75%). Based on these results, it is concluded that DMF preserves sperm motion characteristics and ACI better than GLY, EG, and DMSO, and it is the penetrating cryoprotectant of choice for the cryopreservation of buck sperm in SL extender.

PCR investigation of the vertical transmission of Mycobacterium bovis in Montbéliarde cattle in Gonbad, northeast of Iran

Bovine tuberculosis is an important global zoonosis. The causative agent of the disease is Mycobacterium bovis, belonging to the Mycobacterium tuberculosis complex. This study aimed to identify vertical transmission of Mycobacterium bovis in tuberculin positive pregnant dairy cows referred to the slaughterhouse and commercial sperm used to inseminate them in Gonbad, Gorgan province, Iran, by PCR assay. From March to September 2016, one thousand and seven hundred artificially inseminated cows were subjected to the tuberculin test; then, tuberculin positive cows were referred to the Gonbad slaughterhouse. Samples containing milk, lymph node, placenta, foetal abomasal fluid, and amniotic fluid were prepared from all affected cows and stored at -80 °C until analysis. Bacterial DNA was extracted from all specimens by a commercial kit. Detection was performed by amplifying pncATB gene using special primers via the polymerase chain reaction method. Results of tuberculin test revealed 144 positive cases (8.47%). PCR results for 48 milk samples, 120 biopsy samples, 63 samples of foetuses showed 9, 93 and 43 positive cases, respectively which all belonged to tuberculin positive samples. No positive sperm samples were identified. It was concluded that the infection rate with M. bovis in Montbéliarde cattle was high and also, that vertical transmission was not seen.

Effect of turmeric extract and dimethyl sulfoxide on buffalo semen freezability and fertility

The freeze-thaw process results in structural and functional damages caused by overaccumulation of reactive oxygen species (ROS). Addition of antioxidants to semen extenders is of a great importance to overcome this oxidative damage. The study objective was to evaluate the consequence of using Tris-citric acid fructose egg yolk (TCFY) extender supplemented with a combination of turmeric extract and dimethyl sulfoxide (DMSO) [TTD] on sperm freezability and fertility. From five tubes (each containing 5 mL TCFY), the first tube contained neither turmeric extract nor DMSO and was kept as control. The other four tubes contained 1.5% DMSO plus 100 µL/5 mL, 200 µL/5 mL, 300 µL/5 mL and 400 µL/5 mL turmeric extract. Semen samples were pooled and extended to reach an application of 60×106 sperm/mL (TT1D to TT4D, respectively). Diluted semen was exposed to the freezing protocol. The post cooling results revealed significant improvement in percent of alive spermatozoa in TT1D, significant decrease in sperm abnormalities in all concentrations used, significant improvement in intact acrosome percentage in TT1D, TT2D and TT4D. The post thawing results exhibited significant improvement in sperm motility in TT1D, TT2D and TT4D; significant amelioration of sperm membrane integrity (HOST) in TT1D, TT2D, TT3D and TT4D. Acrosome integrity was maintained in all concentrations as in the control. It was concluded that TT1D revealed the best semen quality in cooled semen; and TT1D, TT2D exhibited the superior post thawing semen quality. In addition, conception rate (CR) of the post-thawed semen was ameliorated in TT1D, TT2D, TT3D and TT4D with TT1D being the best one with this regard.

Ginger and echinacea extracts improve the quality and fertility potential of frozen-thawed ram epididymal spermatozoa

The current study examined the impact of the supplementation of ginger and echinacea extract, as natural antioxidant agents, in freezing extender on the quality and fertility potential of ram epididymal spermatozoa after cryopreservation. Epididymal spermatozoa isolated from Forty testicles, obtained from 20 rams, with motility >80% and total morphological abnormalities <10% were pooled, divided into 7 aliquots and used for cryopreservation. The semen samples were re-suspended with basic Tris egg yolk diluent containing ginger and echinacea extracts (5, 10 and 20 mg/l). The control diluent comprised of only extender and lacked any antioxidant agent. For the determination of sperm quality, frozen straws were thawed after 7-10 days, and then the sperm characteristics were assessed. The supplementation of ginger at a concentration of 10 mg/l, as well as the addition of 10 and 20 mg/l echinacea extract significantly improved total motility and velocity parameters. The status of acrosome integrity and lipid peroxidation significantly improved in spermatozoa when supplemented with 10 mg/l ginger and 20 mg/l echinacea extract. Also, 5 mg/l ginger extract and 20 mg/l echinacea extract significantly improved mitochondrial activity. The highest ratio of the dispersion of sperm chromatin was observed in spermatozoa treated with 10 mg/l ginger extract. The cleavage rate was markedly higher in matured oocytes that were fertilized with frozen spermatozoa treated with 20 mg/l ginger extract and 10 mg/l echinacea. The application of ginger and echinacea extract resulted in improvement in the quality and fertility of frozen-thawed spermatozoa. However, future studies are wanted to elucidate how the active components in these extracts prevent cryo-damages in spermatozoa.

Effect of cryopreservation on delineation of immune cell subpopulations in tumor specimens as determinated by multiparametric single cell mass cytometry analysis

Background

Comprehensive understanding of cellular immune subsets involved in regulation of tumor progression is central to the development of cancer immunotherapies. Single cell immunophenotyping has historically been accomplished by flow cytometry (FC) analysis, enabling the analysis of up to 18 markers. Recent advancements in mass cytometry (MC) have facilitated detection of over 50 markers, utilizing high resolving power of mass spectrometry (MS). This study examined an analytical and operational feasibility of MC for an in-depth immunophenotyping analysis of the tumor microenvironment, using the commercial CyTOF™ instrument, and further interrogated challenges in managing the integrity of tumor specimens.

Results

Initial longitudinal studies with frozen peripheral blood mononuclear cells (PBMCs) showed minimal MC inter-assay variability over nine independent runs. In addition, detection of common leukocyte lineage markers using MC and FC detection confirmed that these methodologies are comparable in cell subset identification. An advanced multiparametric MC analysis of 39 total markers enabled a comprehensive evaluation of cell surface marker expression in fresh and cryopreserved tumor samples. This comparative analysis revealed significant reduction of expression levels of multiple markers upon cryopreservation. Most notably myeloid derived suppressor cells (MDSC), defined by co-expression of CD66b⁺ and CD15⁺, HLA-DR^dim and CD14⁻ phenotype, were undetectable in frozen samples.

Conclusion

These results suggest that optimization and evaluation of cryopreservation protocols is necessary for accurate biomarker discovery in frozen tumor specimens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0192-1) contains supplementary material, which is available to authorized users.

Optimization of the cryopreservation of dromedary camel semen: Cryoprotectants and their concentration and equilibration times

Research into an optimal cryoprotectant, its concentration and equilibration time underlies the successful cryopreservation of dromedary camel spermatozoa. This study assessed the cryo-efficiency of different cryoprotectants, their concentration and equilibration time and any interactions. In experiment 1, semen samples (n = 4 males; 2 ejaculates/male) were frozen using Green Buffer containing one of four cryoprotectants (3% glycerol, ethylene glycol, methyl formamide, dimethyl sulfoxide) and using 4 equilibration times (10 min, 0.5, 1 and 2 h). Glycerol and ethylene glycol provided the best motility recovery rates and different equilibration times were not significant for any cryoprotectant nor were any interactions noted. However different equilibration times were pertinent for improved kinematic parameters BCF and VSL. In experiment 2, glycerol and ethylene glycol were evaluated at 4 concentrations (1.5, 3, 6, 9%) with 0.5 h equilibration (n = 4 males, 3 ejaculates/male). Sperm motility recoveries, kinematics and acrosome status were assessed. Higher values for LIN and STR were found with ethylene glycol. At 0 and 1 h post thaw 3 and 6% of either cryoprotectant resulted in better motility values than 1.5%. Acrosome integrity was compromised at 9% cryoprotectant. There were interactions between cryoprotectant and concentration in total motility at 0 and 1 h. For glycerol, total motility recoveries were best at 3-9%; for ethylene glycol 1.5-6% were best at 0 h and 3-6% at 1 h. In conclusion, 3-6% glycerol or ethylene glycol offered the best cryoprotection for camel sperm while different equilibration times were not critical.

[Effects of some extenders and monoamines on sperm cryopreservation in tree shrews (Tupaia belangeri)]

The tree shrew may be an important experimental animal for disease models in humans. The effects of some extenders and momamines on sperm cryopreservation will provide helpful data for experimentation of strains and conservation of genetic resources in tree shrews. Epididymal sperm were surgically harvested from male tree shrews captured around Kunming, China and sperm motility, acrosome integrity and fertility were assessed during cryopreservation. In Experiment 1 eight extenders (TTE, TCG, TCF, TTG, BWW, BTS, DM, and SR) supplemented with 0.4 mol/L DMSO were used to dilute the sperm: only TTE, DM and SR showed no differences in motility and acrosome integrity compared to fresh controls after equilibration. After freezing and thawing, sperm in any extender showed lower motility than fresh control and sperm in DM showed higher motility than other groups. However, BWW produced the lowest motility. For acrosome integrity, TTE and DM showed higher than BWW, BTS and SR after equilibration. The parameter in DM was higher than other groups (except TTE) after thawing. In Experiment 2 four penetrating cryoprotectant agents (CPA) [dimethyl-formamide (DF), formamide (F), dimethylacetamide (DA), and acetamide (A)] at 0.2 mol/L, 0.4 mol/L, 0.8 mol/L, and 1.2 mol/L, respectively were added to the DM extender. Motility showed no difference among CPA groups and non-CPA group (control) after equilibration, but all thawed sperm showed lower values in motility and acrosome integrity than pre-freezing groups. However, sperm in 0.8 mol/L DF and 0.4 mol/L DMSO showed higher values in both parameters than that in other CPA groups (P>0.05). In Experiment 3 the fertilization rate of oocytes inseminated with 0.4mol/L DMSO (50%) were higher than that with 0.8mol/L DF (16%). In conclusion, non-ion extenders supplemented with egg yolk may be better for sperm cryopreservation in tree shrews and cryoprotectant effects of monoamines agents should be further studied in this species.