Comparing sugar type supplementation for cryopreservation of boar semen in egg yolk based extender

The Effect of κ-Carrageenan on Porcine Sperm Cryo-Survival

κ-Carrageenan is a sulfated polysaccharide from red seaweed with substantial antioxidant activities. This study aimed to investigate the effect of κ-Carrageenan treatment on frozen-thawed (FT) porcine semen quality. Therefore, the spermatozoa were diluted and cryopreserved in a freezing extender supplemented with 0 (control), 0.2, 0.4, 0.6, and 0.8 mg/mL κ-Carrageenan. Sperm kinematics were assessed immediately after thawing (AT) and post-incubation for 120 min. The viability, acrosome integrity, lipid peroxidation, mitochondrial membrane potential (MMP), and intracellular caspase activity were measured AT. The results indicated that 0.2 mg/mL κ-Carrageenan increased total and progressive motility AT and post-incubation for 120 min (p < 0.05). Moreover, the viable sperm percentage and MMP after 0.2 mg/mL treatment were higher than those after control and other κ-Carrageenan concentration treatments. The proportion of acrosome-intact spermatozoa was significantly higher after 0.2 and 0.4 mg/mL κ-Carrageenan treatment than that after control and other κ-Carrageenan concentration treatments. The intracellular caspase activity was not significantly different among the experimental groups. However, the MDA concentration after 0.2 mg/mL κ-Carrageenan treatment was lower (p < 0.05) than that after the control treatment. Taken together, adding κ-Carrageenan to the porcine semen freezing extender improved the FT sperm quality mainly by influencing membrane stability and protecting against oxidative stress.

Freeform Cell-Laden Cryobioprinting for Shelf-Ready Tissue Fabrication and Storage

One significant drawback of existing bioprinted tissues is their lack of shelf-availability caused by complications in both fabrication and storage. Here, we report a cryobioprinting strategy for simultaneously fabricating and storing cell-laden volumetric tissue constructs through seamlessly combining extrusion bioprinting and cryopreservation. The cryobioprinting performance was investigated by designing, fabricating, and storing cell-laden constructs made of our optimized cryoprotective gelatin-based bioinks using a freezing plate with precisely controllable temperature. The in situ freezing process further promoted the printability of cell-laden hydrogel bioinks to achieve freeform structures otherwise inconvenient with direct extrusion bioprinting. The effects of bioink composition on printability and cell viability were evaluated. The functionality of the method was finally investigated using cell differentiation and chick ex ovo assays. The results confirmed the feasibility and efficacy of cryobioprinting as a single-step method for concurrent tissue biofabrication and storage.

Oxidative and nitrosative stress in frozen-thawed pig spermatozoa. II: Effect of the addition of saccharides to freezing medium on sperm function

Saccharides have bioprotective properties, with a high capacity to preserve biological proteins and membranes during sperm cryopreservation. The aim of this study was to evaluate how replacing the lactose of cryopreservation media by sucrose (SUC) or trehalose (TRE) at concentrations of 0.2 M (SUC-1 and TRE-1) and 0.25 M (SUC-2 and TRE-2) affects frozen/thawed pig spermatozoa. The media used were composed of medium A (saccharide/egg yolk) and B (saccharide/egg yolk/glycerol), their osmolality being determined prior to freezing. Cell viability, membrane lipid disorder, acrosome integrity, mitochondrial membrane potential (MMP), lipid peroxidation, thiol group oxidation, total reactive oxygen species (ROS), peroxynitrite and superoxide anion (O₂^●-) were determined through flow cytometry; total motility (TM), progressive motility (PM) and kinetic parameters motility were determined immediately after thawing (T0) and again 30 (T30) and 60 (T60) minutes later. The SUC-2 and TRE-2 groups maintained viability significantly and presented fewer lipid membrane disorders, respectively, both with a significant increase in MMP. The production of O₂^●- and peroxynitrite was lower in the TRE-2 groups compared to the control (P < 0.05). Total motility at T0 was greater in the TRE-2 group (P < 0.05). Sperm kinetics was not affected by the treatment. The use of saccharides SUC and TRE at a concentration of 0.25 M improves sperm quality, so that both non-penetrating cryoprotectants can be utilized in pig sperm freezing media.

Cryopreservation of canine spermatozoa using a skim milk-based extender and a short equilibration time

Although useful spermatozoa cryopreservation techniques have been established, long-term equilibration seems to be required before freezing the spermatozoa of many species, including dogs. The fertility of cryopreserved dog spermatozoa from five males for a reduced equilibration period (0, 30, 60, 120 and 180 min) in a skim milk (SM)-based extender containing raffinose was evaluated in the present study. When the sperm was diluted with the extender at room temperature (RT) and cryopreserved without equilibration, the proportion of total motile spermatozoa (TMS) after thawing was lower (27%) than when the sperm was equilibrated for 30 min (33%), 60 min (32%), 120 min (44%; p < .05) or 180 min (29%). The proportion of TMS increased as the equilibration time increased and peaked at 120 min. Acrosome integrity was significantly lower in the cryopreserved spermatozoa that had not undergone the initial equilibration than in the equilibrated spermatozoa (p < .05). The normal rate of acrosomes increased with the extension of the first equilibration and peaked at 120 min. When frozen-thawed spermatozoa that had been diluted at RT and subjected to an initial equilibration lasting 60 or 180 min were transcervically inseminated into recipients, there were no differences in the delivery rate, litter size or breeding efficiency. In the cryopreservation of canine spermatozoa using a SM-based extender, even if the initial equilibration time was shortened to 60 min, the results were comparable to those obtained when the conventional method (with an initial equilibration time of 180 min) was used.

Cryopreservation Effects on Ram Sperm Ultrastructure

Cryoprotectants are known to have protective effects against cryodamage to spermatozoa. In this study, the cryoprotective effects of two cryoprotectants (glycerol, ethylene glycol) and cryoprotectants/trehalose combinations on frozen-thawed ram spermatozoa were investigated at the ultrastructural level. For this purpose, ejaculates collected from Konya Merino rams were pooled and diluted with a tris-based extender containing additives, including 5% glycerol, 3% glycerol +60 mM trehalose, 1.5% glycerol +100 mM trehalose, 5% ethylene glycol, 3% ethylene glycol +60 mM trehalose, and 1.5% ethylene glycol +100 mM trehalose. They were all cooled to 5°C and then frozen in 0.25 mL French straws in liquid nitrogen. The samples were thawed at 37°C and centrifuged to remove the diluents. Then, they were processed using a scanning transmission electron microscope. In the statistical analysis, the number of ultrastructurally cryodamaged and intact spermatozoa were counted in longitudinal and transverse ultrathin sections in all groups by electron microscopic examination. The amount of intact spermatozoa in the groups containing 5% ethylene glycol and 1.5% ethylene glycol +100 mM trehalose was found to be higher than other groups (p < 0.05). As a result, it was suggested that the groups of 5% ethylene glycol and 1.5% ethylene glycol +100 mM trehalose provided the highest protection for the ultrastructural morphology of frozen-thawed Konya Merino ram spermatozoa among the groups.

Membrane fusion and infection abilities of baculovirus virions are preserved during freezing and thawing in the presence of trehalose

Budded viruses (BVs) of baculovirus such as Autographa californica nucleopolyhedrovirus (AcNPV) have recently been studied as biological nanomaterials, and methods for their longer-term storage without deterioration would be desirable. The cryopreservation of virions with a naturally occurring saccharide like trehalose as a cryoprotectant is known to be useful for maintaining the viral structure and function. In this study, we examined how useful trehalose is as protectant for BV cryopreservation during repeated freeze-thaw cycles: 1) membrane fusion between liposomes (multilamellar vesicles, MLVs) and BVs, 2) infection of insect culture cells (Sf9 cells) by RFP-expressing BVs, and 3) morphologies of these BVs were investigated by fluorescent dequenching assay, fluorescence microscopy, and transmission electron microscopy (TEM), respectively. The results suggest that the BVs deteriorate in quality with each freeze-thaw cycle, and this deterioration can be diminished with the use of trehalose to an extent similar to that seen with storage on ice.

Fertilizing ability of canine spermatozoa cryopreserved with skim milk-based extender in a retrospective study

We previously reported that skim milk (SM) is an effective cryoprotectant for cryopreservation of canine spermatozoa instead of egg yolk (EY), which is the conventional cryoprotectant. In this study, the fertilizing ability and practical use of frozen canine spermatozoa prepared with SM were evaluated by transcervical insemination. Frozen-thawed spermatozoa were inseminated one to four times on days 2-9 after the LH surge. In SM group, a single transcervical insemination (TCI) on Day 5 led to higher delivery rate (83%) than any other days (33%-50%) post-LH surge. In EY group, delivery rate in double TCI on days 5 and 6 (71%) was higher compared to any other experimental groups (0%-44%). Regardless of single or double, TCI on Day 5 or Day 6 led to higher litter sizes in SM or EY groups, respectively. The breeding efficiency and litter size of single TCI on Day 5 (4.2) and double TCI on Day 5 and Day 6 (3.7) were significantly higher than in the other experimental groups in SM and EY groups, respectively (p < .05). These findings suggest that skim milk is a suitable alternative to egg yolk for cryopreservation of canine spermatozoa, and the suitable timing for insemination might be on Day 5 post-LH surge.

Effects of difructose dianhydride (DFA)-IV on in vitro fertilization in pigs

Difructose dianhydride IV (DFA-IV) is produced from levan, which is a natural polysaccharide that belongs to the fructan family, through the activity of levan fructotransferase (LF) derived from microorganisms. Recently, DFA-IV has been expected to have diverse applications in the food and medical industry. Here, we examined the potential application of DFA-IV forin vitro fertilization (IVF) in pigs. In the assessment of acrosomal integrity during incubation, intact acrosomal or viable spermatozoa were highly sustained in 0.1% or 0.25% DFA-IV (69.8%-70.8%,P<0.05). Reactive oxygen species (ROS) levels during sperm incubation decreased following the addition of DFA-IV, and 0.1%-0.5% DFA-IV in particular significantly decreased ROS production relative to that seen with no addition or 0.75% DFA-IV. Total fertilization (mono+ polyspermic oocyte) rate was significantly higher in the addition of 0.1% DFA-IV (94.2%) than with other concentrations (71.8%-86.7%,P<0.05). When using reduced IVF times and lower sperm numbers, we found that addition of 0.1%–0.5% DFA-IV significantly increased the fertilization rate (P<0.05). Fertilized oocytes treated with 0.1% DFA-IV exhibited higher embryonic development and blastocyst formation than those treated with other concentrations (P<0.05). Consequently, the addition of DFA-IV during IVF improved fertilization and embryonic development, suggesting the possible use of novel sugars for enhancement of assisted reproductive technology (ART) in mammals.

Trehalose, an easy, safe and efficient cryoprotectant for the parasitic protozoan Trypanosoma brucei

Trehalose, a non-permeating cryoprotective agent (CPA), has been documented as less toxic and highly efficient at cryopreserving different kinds of cells or organisms. In the present study, trehalose was evaluated for its application in cryopreservation of both Trypanosoma brucei procyclic and bloodstream form cells. The cryopreservation efficiency was determined by the motility of trypanosomes after thawing, as well as a subsequent recovery and infectivity assessment. The viability of trypanosomes from cultivation that were frozen in a serial concentrations of trehalose showed similar results to classical CPAs of glycerol and DMSO. Nevertheless, trypanosomes cryopreserved in 0.2M trehalose showed the best growth characteristic during subsequent cultivation. In addition, CPA cocktails with trehalose and permeating CPA glycerol or DMSO were developed and evaluated. Interestingly, trypanosomes in host (mouse) blood cryopreserved in 0.4M trehalose plus 5% glycerol showed higher infectivity than those preserved in trehalose/DMSO cocktails as well as individually. Further investigations showed that, in comparison with slow freezing at -80°C, flash freezing in liquid nitrogen provided better cryopreservation for bloodstream form cells than slow freezing. In conclusion, trehalose is an easy, safe and efficient CPA for cryopreservation of T. brucei and potentially for other protozoan species and cells.

Recent Advances in Boar Sperm Cryopreservation: State of the Art and Current Perspectives

While sperm cryopreservation is the best technology to store boar semen for long-term periods, only 1% of all artificial inseminations (AI) conducted worldwide are made using frozen-thawed boar sperm. With the emergence of long-term extenders for liquid storage, the use of cryopreserved sperm in routine AI is less required. However, banks of boar semen contain cryopreserved sperm and planning inseminations in AI centres may benefit from the use of frozen-thawed semen. Therefore, there is an interest in the use of this technology to preserve boar sperm. In this regard, although the first attempts to cryopreserve boar semen date back to the seventies and this technology is still considered as optimal, some relevant improvements have been made in the last decade. After giving a general picture about boar sperm cryodamage, the present review seeks to shed light on these recent cryopreservation advances. These contributions regard to protein markers for predicting ejaculate freezability, sperm selection prior to start cryopreservation procedures, additives to freezing and thawing extenders, relevance of the AI-technique and insemination-to-ovulation interval. In conclusion, most of these progresses have allowed counteracting better boar sperm cryodamage and are thus considered as forward steps for this storage method. It is also worth noting that, despite being lower than fresh/extended semen, reproductive performance outcomes following AI with frozen-thawed boar sperm are currently acceptable.

Methods for Improving In Vitro and In Vivo Boar Sperm Fertility

Fertility of boar spermatozoa is changed after ejaculation in vivo and in vitro. During processing for in vitro fertilization (IVF), although spermatozoa are induced capacitation, resulting in a high penetration rate, persistent obstacle of polyspermic penetration is still observed with a high incidence. For artificial insemination (AI), we still need a large number of spermatozoa and lose a majority of those in the female reproductive tract. Fertility of cryopreserved boar spermatozoa is still injured through freezing and thawing process. In the present brief review, factors affecting fertility of boar sperm during IVF, AI and cryopreservation are discussed in the context of discovering methodologies to improve it.

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.

Trehalose in glycerol-free freezing extender enhances post-thaw survival of boar spermatozoa

Cryopreservation of boar semen is still considered suboptimal due to lower fertility as compared with fresh samples when glycerol, a permeating cryoprotectant, is used. Trehalose is a non-permeable cryoprotectant and nonreducing disaccharide known to stabilize proteins and biologic membranes. The aim of this study was to evaluate the cryosurvival and in vitro penetrability of boar spermatozoa when glycerol was replaced with trehalose in a freezing extender. Ejaculated Berkshire semen samples were diluted in egg yolk-based freezing extender containing glycerol (100 mM) or trehalose (0, 50, 100, 150, 200 and 250 mM) and cryopreserved using a straw freezing procedure. Thawed samples were analyzed for motility, viability, mitochondrial membrane potential (MMP), and acrosome integrity. In experiment 2, penetrability of spermatozoa cryopreserved with 100 mM glycerol or trehalose was examined. Replacement of cryoprotectant glycerol (100 mM) with trehalose had no effect on sperm viability, but replacing it with 100 mM trehalose improved motility, MMP and acrosome integrity significantly. Sperm motility and MMP were considerably higher in 100 mM trehalose, whereas the acrosome integrity was substantially higher in 100–250 mM trehalose. The in vitro penetration rate was also significantly higher in spermatozoa cryopreserved with trehalose (61.3%) than in those cryopreserved with glycerol (43.6%). In conclusion, 100 mM non-permeable trehalose can be used to replace glycerol, a permeating cryoprotectant, for maintenance of better post-thaw quality of boar spermatozoa.

Comparing ethylene glycol with glycerol and with or without dithiothreitol and sucrose for cryopreservation of bull semen in egg-yolk containing extenders

There are few studies performed for investigating the roles of different ratio and cryoprotectants with dithiothreitol or sucrose on sperm motility characteristics and antioxidant capacities of post-thawed bull spermatozoa. The objectives of this study were to compare glycerol (G) and ethylene glycol (EG) at different concentrations as cryoprotectants and dithiothreitol (D) or sucrose (S) (with/without) as antioxidants in Tris extender for cryopreservation of bull semen. Twenty-four ejaculates obtained from three bulls were included in the study. Each ejaculate was split into four equal aliquots and diluted using both of the Tris extenders with glycerol (5% or 7%) or ethylene glycol (3% or 5%). After that, each extenders were split into three equal aliquots and diluted using both of the dithiothreitol 5mM or sucrose 25 mM, and control (without additives) was cooled to 4 °C and frozen in 0.25-ml French straws. when compared to control, different doses cryoprotectants and antioxidants addition no significantly increased the percentages of post-thaw sperm progressive and motitilities, acrosome abnormality and plasma membrane integrity (P>0.05). However, EG3+S yielded the greatest percentages of the total abnormality (P<0.05). As regard to antioxidant activities G7 and EG5 led to lowest MDA activity with or without D or S but, these results were not supported to the GPx activity (P<0.01). The sperm motion characteristics such as VAP, VCL, ALH and BCF gave significantly different results (P<0.05). When compared the DNA integrity, different doses cryoprotectants without antioxidants addition significantly increased the percentages of the tail intensity and tail moment (P<0.05). There were no significant differences observed in non-return rates among all treatment groups (P>0.05).

Comprehensive profiling of accessible surface glycans of mammalian sperm using a lectin microarray

It is well known that cell surface glycans or glycocalyx play important roles in sperm motility, maturation and fertilization. A comprehensive profile of the sperm surface glycans will greatly facilitate both basic research (sperm glycobiology) and clinical studies, such as diagnostics of infertility. As a group of natural glycan binders, lectin is an ideal tool for cell surface glycan profiling. However, because of the lack of effective technology, only a few lectins have been tested for lectin-sperm binding profiles. To address this challenge, we have developed a procedure for high-throughput probing of mammalian sperm with 91 lectins on lectin microarrays. Normal sperm from human, boar, bull, goat and rabbit were collected and analyzed on the lectin microarrays. Positive bindings of a set of ~50 lectins were observed for all the sperm of 5 species, which indicated a wide range of glycans are on the surface of mammalian sperm. Species specific lectin bindings were also observed. Clustering analysis revealed that the distances of the five species according to the lectin binding profiles are consistent with that of the genome sequence based phylogenetic tree except for rabbit. The procedure that we established in this study could be generally applicable for sperm from other species or defect sperm from the same species. We believe the lectin binding profiles of the mammalian sperm that we established in this study are valuable for both basic research and clinical studies.

Effect of different monosaccharides and disaccharides on boar sperm quality after cryopreservation

The aim of the present study was to evaluate the cryoprotectant effect of different non-permeating sugars for boar sperm. Pooled semen from three boars was used for the experiments. In the first experiment, the sperm quality of boar sperm cryopreserved with an egg-yolk based extender supplemented with different monosaccharides (glucose, galactose or fructose) was compared to a control cryopreserved in lactose-egg yolk extender. In the second experiment, the effect of five disaccharides (lactose, sucrose, lactulose, trehalose or melibiose) on boar sperm cryosurvival was studied. Several sperm quality parameters were assessed by flow cytometry in samples incubated for 30 and 150 min at 37°C after thawing: percentages of sperm with intact plasma membrane (SIPM), sperm presenting high plasma membrane fluidity (HPMF), sperm with intracellular reactive oxygen substances production (IROSP) and apoptotic sperm (AS). In addition, the percentages of total motile (TMS) and progressively motile sperm (PMS) were assessed at the same incubation times with a computer-assisted sperm analysis system. Freezing extenders supplemented with each of the monosaccharide presented smaller cryoprotective effect than the control extender supplemented with lactose (P<0.05). However, from the three monosaccharides tested, glucose provided the best sperm quality after freezing-thawing. With respect to the disaccharides studied, samples frozen with the extender supplemented with lactulose exhibited in general the lowest sperm quality, except for the percentage of capacitated sperm, which was highest (P<0.05) in the samples cryopreserved with the trehalose extender. Our results suggest that disaccharides have higher cryoprotective effect than monosaccharides, although the monosaccharide composition of the disaccharides is also important, since the best results were obtained with those disaccharides presenting glucose in their composition.

The effects of different sugars on motility, morphology and DNA damage during the liquid storage of rat epididymal sperm at 4°C

This study evaluated the protective effects of supplementation with three different sugars on the motility, morphology and DNA integrity of rat epididymal sperm chilled and stored at 4°C Epididymides were obtained from each donor. Rat epididymal sperm was diluted in Ham's F10 plus raffinose, Ham's F10 plus trehalose, Ham's F10 plus fructose, and Ham's F10 medium for control purposes. Thereafter, the extended sperm were chilled and stored in liquid form at 4°C. Sperm motility, morphological abnormalities and DNA damage were determined at 0 and 12h after chilling. No significant difference was observed in any of the parameters evaluated at 0h, before storage (P>0.05). After 12h of storage, all sugar additives led to statistically higher motility, normal sperm morphology and DNA integrity in comparison to the control group. Raffinose gave the best motility percentages (32.86±1.84%) after 12h of storage at 4°C, compared to the other groups (P<0.001). In conclusion, Raffinose, trehalose and fructose provided a better protection of sperm functional parameters against chilling injury, in comparison to the control group.

Comparative quality assessment of buffalo (Bubalus bubalis) semen chilled (5°C) in egg yolk- and soya milk-based extenders

Egg yolk-Tris is most commonly used semen extender; however, its use involves hygienic risk, interference with fertility and poor microscopic examination. Therefore, replacement of egg yolk with a plant-based component with protective effects on spermatozoa would be advantageous. In present study, we observed effect of soya milk-based extenders on dilution and liquid preservation of Murrah buffalo bull semen at 5°C up to 72 h in comparison with conventional egg yolk-Tris extender (Ext.1). In experiment one, a total of 32 buffalo semen ejaculates from four animals were extended and preserved at 5°C for 72 h in soya milk-based extender (Ext.2) with different percentages (10%, 15%, 20%, 25% and 30%) of soya milk for optimization of soya milk concentration. Semen quality was assessed for individual motility, viability, membrane integrity and acrosome integrity at 0, 24, 48 and 72 h of liquid preservation. The results of experiment one indicated that 25% soya milk is an optimum concentration for buffalo bull semen extender preparation. A modified method was used to prepare another soya milk-based extender (Ext.3). In the second experiment, two soya extenders (Ext.2 and 3) with optimized concentration (25%) of soya milk were comparatively assessed with egg yolk-Tris extender (Ext.1) for semen quality parameters at 0, 24, 48 and 72 h of liquid preservation. The individual sperm motility at 0 and 24 h following dilution were found non-significant among extenders. However, after 48 h of dilution, individual motility in Ext.3 was observed significantly (p < 0.05) higher than Ext.1. After 24, 48 and 72 h of dilution sperm membrane integrity in Ext.3 was found significantly (p < 0.05) higher than Ext.1. Overall, comparative evaluation of sperm parameters obtained revealed that Ext.3 containing 25% soya milk can be used as a substitute of egg yolk-based extender for buffalo semen liquid preservation.