Canine sperm vitrification with sucrose: effect on sperm function

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.

Equilibration time improves the sperm variables of wild ruminant ejaculated and epididymal sperm cryopreserved by ultra-rapid freezing

This work examines the effect of equilibration time with extender on ultra-rapidly frozen-thawed wild ruminant epididymal (origin: Iberian ibex) and ejaculated (origin: mouflon) sperm variables. Sperm samples were prepared either without prior equilibration, or equilibrated for 30 min before freezing. Higher quality (p < 0.05) frozen-thawed spermatozoa were obtained when equilibration was allowed, for ejaculated sperm in terms of sperm motility, acrosome apical ridge integrity, sperm viability, and percentage of normal cells, and for epididymal sperm in terms of linearity and straightness of sperm movement. The sperm head area, head perimeter, head length and head width were smaller (p < 0.01) in the equilibrated than non-equilibrated frozen-thawed epididymal sperm; no such dimensional changes were recorded for ejaculated sperm. In conclusion, equilibration prior to ultra-rapid freezing improves the cryoresistance of sperm cells, although viable sperm cells can be obtained without equilibration. The epididymal sperm showed greater cryoresistance, supporting the idea that it is more resistant to freeze-thawing than ejaculated sperm.

Ultra-Rapid Freezing Using Droplets Immersed into Liquid Nitrogen in Bull Sperm: Evaluation of Two Cryoprotective Disaccharides and Two Warming Temperatures

The present study analyzes the effects of different disaccharide concentrations and two thawing temperatures on the characteristics of ultrarapid frozen (URF) bovine sperm, compared with conventional slow-frozen (CF) sperm. For URF sperm, samples were diluted in media comprising 2% bovine serum albumin (BSA) and various nonpermeable cryoprotectants. Five groups were compared: control (without cryoprotectant), sucrose 0.15 M, sucrose 0.3 M, trehalose 0.15 M, and trehalose 0.3 M. In addition, the influence of warming temperatures, 37°C and 65°C, was analyzed. The aspect of different diluents (by drops) immersed in liquid nitrogen was also evaluated. Sperm quality was assessed by measuring motility, viability, acrosome status, and membrane lipid peroxidation (LPO). Moreover, the cryoresistance rate (CR) was determined. The drops immersed in liquid nitrogen showed that crystallization occurred, but not vitrification. CF sperm exhibited significantly higher scores for total motility (TM) and progressive motility (PM), viability, and acrosome integrity, in contrast with URF samples. Cryoprotectants for URF sperm showed a significant (p ≤ 0.05) influence on the TM and PM, viability, acrosome integrity, and CR, but not on LPO. Sperm viability was reduced after ultrarapid freezing, and the control samples were observed to have significantly lower values than those treated with disaccharides. Samples supplemented with 0.3 M sucrose exhibited higher LPO when they were thawed at 37°C. In short, a limited number of spermatozoa were able to maintain their motility and other functional attributes after ultrarapid freezing, but disaccharides showed a moderate protective effect. Samples with trehalose and sucrose at 0.15 and 0.3 M, respectively, showed higher sperm quality than samples containing only BSA. In sum, the function of spermatozoa was moderately maintained when disaccharides were used for ultrarapid freezing, although motility was significantly reduced. In addition, thawing temperatures did not modify the sperm values, suggesting that the easier procedure, that is, 37°C for 30 seconds, can be used.

Successful recovery of motile and viable boar sperm after vitrification with different methods (pearls and mini straws) using sucrose as a cryoprotectant

Vitrification of sperm by direct contact with liquid nitrogen is increasing in popularity as an alternative to conventional (slow) freezing. Although slow freezing is very challenging in boar sperm cryopreservation, this is currently the standard method used. We compared vitrification in "pearls" and in "mini straws" using the in vitro fertilization media Porcine Gamete Media with 0.3 M sucrose with the standard (slow) method used to preserve boar sperm. Both vitrification methods reduced the viability of the sperm sample more than slow freezing (42.2 ± 4.3% total motility and 71.4 ± 2.3% alive), however, both protocols allowed for the successful recovery of the sperm samples. By comparing two different methods of vitrification and two different methods of post-thaw preparation we were able to determine the optimal vitrification-thaw protocol for boar sperm. When comparing pearls and mini-straws, the smaller liquid volume associated with pearls had a positive effect on the survivability of the samples, reducing sperm DNA damage (1.2 ± 0.2% vs. 5.1 ± 0.1.7%) and preserving motility (26.15 ± 2.8% vs 9.39 ± 0.9%) after thawing. In conclusion, the pearl method was the most suitable of the vitrification techniques for use with boar sperm.

Epididymal Spermatozoa Show Higher Cryoresistance to Vitrification Process Than Ejaculated Spermatozoa in Dogs

The aim of this study was to investigate differences in the sperm response to a vitrification-warming process between ejaculated and epididymal dog spermatozoa, and to evaluate the efficacy of an animal protein-free extender for vitrification of both types of sperm cells. Vitrified-warmed spermatozoa from the epididymis showed greater (p < 0.001) progressive motility and total motility values than ejaculated spermatozoa, regardless of the diluent. The vitrification procedure returned better results for viability and intact acrosome when human tubal fluid (HTF®) was used (25.10 ± 7.90 and 56.50 ± 6.7, respectively) compared with Tris-Citric acid-Glucose (TCG) (15.20 ± 4.70 and 43.70 ± 7.9, respectively) in ejaculated samples. Similarly, higher total motility (34.5 ± 4.5) was observed in HTF postwarmed samples compared with TCG-treated samples (19.52 ± 5.1). The interaction source (epididymis, ejaculated) × extender had a significant effect (p < 0.001) on the values of total motile spermatozoa after warming. HTF-based extender improved (p < 0.001) total motility values in epididymal samples, but not in ejaculated samples. In conclusion, epididymal spermatozoa show higher cryoresistance to the vitrification process than ejaculated spermatozoa in dogs. The use of HTF is adequate for both ejaculated and epididymal canine sperm vitrification.

Canine sperm vitrification with nonpermeable cryoprotectants and coconut water extender

This study was aimed to assess the efficiency of coconut water extender with addition of soy lecithin and sucrose as nonpermeable cryoprotectants for canine semen vitrification, using a simple method that yields a high survival rate of spermatozoa for clinical use. Twelve ejaculates from 12 adult normozoospermic dogs were collected separately by digital manipulation and only the second semen fraction was used in this study. After evaluation of volume, concentration, viability, total and progressive motility, velocity parameters and morphology, semen was diluted with a coconut water extender (50% (v/v(volume per volume)) coconut water, 25% (v/v) distilled water and 25% (v/v) 5% anhydrous monosodium citrate solution) with addition of soy lecithin and fructose at 1% and 0.25M sucrose until final concentration of 100x10⁶ spermatozoa/ml. After equilibration at 5ºC for 60 minutes, semen was vitrified by "direct dropping method" into liquid nitrogen in spheres with a volume of 30 μl. After a week of storage the spheres were devitrified as three of them were dropped into 0.5 mL of CaniPlus AI medium (Minitüb, Germany), which was previously warmed in a water bath at 42ºC for 2 minutes and evaluated about the above mentioned parameters. It was found that vitrification resulted in a lower percentage of viable sperms, normal morphology, total and progressive motilities (p<0.05), but most of velocity parameters (VCL, VSL, VAP, LIN, ALH and BCF) did not differ (p>0.05) compared to fresh semen samples. In conclusion, our results demonstrate that vitrification with coconut water extender with addition of 1% soy lecithin and 0.25M sucrose as cryoprotectants, has an excellent potential for routine canine sperm cryopreservation.

Kinetic vitrification: concepts and perspectives in animal sperm cryopreservation

Sperm cryopreservation is an important tool for genetic diversity management programs and the conservation of endangered breeds and species. The most widely used method of sperm conservation is slow freezing, however, during the process, sperm cells suffer from cryoinjury, which reduces their viability and fertility rates. One of the alternatives to slow freezing is vitrification, that consist on rapid freezing, in which viable cells undergo glass-like solidification. This technology requires large concentrations of permeable cryoprotectants (P- CPA's) which increase the viscosity of the medium to prevent intracellular ice formation during cooling and warming, obtaining successful results in vitrification of oocytes and embryos. Unfortunately, this technology failed when applied to vitrification of sperm due to its higher sensitivity to increasing concentrations of P-CPAs. Alternatively, a technique termed 'kinetic sperm vitrification' has been used and consists in a technique of permeant cryoprotectant-free cryopreservation by direct plunging of a sperm suspension into liquid nitrogen. Some of the advantages of kinetic vitrification are the speed of execution and no rate-controlled equipment required. This technique has been used successfully and with better results for motility in human (50-70% motility recovery), dog (42%), fish (82%) and donkey (21.7%). However, more studies are required to improve sperm viability after devitrification, especially when it comes to motility recovery. The objective of this review is to present the principles of kinetic vitrification, the main findings in the literature, and the perspectives for the utilization of this technique as a cryopreservation method.

Ultra-Rapid Freezing Preserves Morphofunctional Integrity and Fertilizing Ability of Epididymal Cat Spermatozoa

Vitrification and ultra-rapid freezing, which are more commonly used for oocytes and embryos, have recently been applied to spermatozoa in an attempt to make semen cryopreservation in field conditions easier compared to conventional freezing. It is well-known that in case of unexpected death of rare and wild animals, preserving epididymal spermatozoa from isolated testicles represents a great chance of salvaging male germplasm for future use in assisted reproductive technologies. The aim of this study was to evaluate the morphofunctional integrity of cat epididymal spermatozoa ultra-rapid frozen in pellets or straws with two different extenders [E1 (Tris buffer with 20% egg yolk and 0.25 M sucrose) or E2 (Ham's F10 with 1% bovine serum albumin and 0.4 M sucrose)] and to test whether spermatozoa preserved by the best combination were able to fertilize oocytes and produce embryos in vitro by intracytoplasmic sperm injection (ICSI) of in vitro matured cat oocytes. The results showed that E1 and E2 in straw or pellet were comparable (at warming, about 30% normal morphology, 45% intact membranes, and 20% intact acrosomes), except for post-warming motility that was better maintained along time by E1 pellet (21.7 ± 7.4% at warming and 3.6 ± 2.9% after 6 h). Such spermatozoa could fertilize conspecific oocytes and support embryonic development (cleavage 35.5%) as well as frozen control spermatozoa (cleavage 54.29%, p = 0.22). In conclusion, cat epididymal spermatozoa better maintained their morphofunctional features after ultra-rapid freezing with E1 and could successfully produce embryos in vitro after ICSI. This underscores their usefulness as cryobanked material for fertility and biodiversity preservation purposes.

Semen collection, evaluation, and cryopreservation in the bonobo (Pan paniscus)

Background

Captive breeding of bonobos (Pan paniscus) has proven to be successful, but maintaining genetic diversity remains a challenge. Cryopreservation of semen is an important potential tool to maintain genetic diversity by preserving current genetic material for future use, as well as facilitating the transport and exchange of genetic material. This study aimed to develop a protocol for semen collection and cryopreservation in the bonobo. Semen was collected from four healthy adult bonobos under general anesthesia during management translocation procedures. Semen collection utilizing urethral catheterization was not successful (n = 1), however, all males (n = 4) responded well to rectal probe electro-ejaculation. Immediately after collection, ejaculates were evaluated for color and admixtures, volume, motility, and concentration. Eosin-Nigrosin staining was prepared to evaluate morphology and viability. Ejaculates were split into two equal volumes and cryopreserved in two different extenders, using a one-step and a two-step approach. Ejaculates were gradually cooled to 4 °C in two hours, subsequently stored in liquid nitrogen vapor for twenty minutes (0.25 ml straws), and finally dropped into liquid nitrogen.

Results

Pre-freeze evaluation showed thick, white samples with an average ejaculate volume of 450 µl (100-1000 µl), total motility of 59% (40–80%), viability of 69% (38–85%) and 58% (46–72%) normal spermatozoa. Mainly head (22%) and tail (19%) defects were detected on the Eosin-Nigrosin stain. Ejaculates were highly concentrated, nevertheless, due to the coagulum that caused high viscosity and non-homogenous fractions, only estimations of concentration could be made (1000 million/ml). After 24 h of storage, the post-thaw evaluation showed a loss of quality with an average post-thaw total motility of 15% (5–25%) using the one-step freezing medium, and 19% (5–30%) using the two-step medium. Average post-thaw viability was 15% (4–24%) and 21% (15–29%), respectively.

Conclusions

This report on ejaculates from bonobos obtained by rectal probe electro-ejaculation shows that semen parameters of this species are not completely similar to those of its sibling species, the chimpanzee. Further studies are necessary to develop an optimal protocol for the processing and cryopreservation of bonobo spermatozoa.

Vitrification of Iberian wolf (Canis lupus signatus) sperm: A possible alternative to conventional cryopreservation

Sperm vitrification is a simple, inexpensive method that allows the cryopreservation of sperm in the field and for endangered species is a useful alternative to conventional freezing. The study, therefore, is focused on the suitability of vitrification for cryopreserving Iberian wolf sperm and utilizing plasma testosterone concentration as a marker for procedure efficacy. Sperm and blood samples were collected from 17 wolves. There were 14 samples suitable for cryopreservation (12 ejaculated and two epididymal). Immediately after collection, these samples were proportioned into two aliquots for conventional freezing using a Tris-citric acid-glucose based extender (TCG) or vitrification utilizing an animal protein free extender (HTF®). Vitrification occurred by directly plunging a sperm suspension into liquid nitrogen. Sperm were assessed for motility, membrane integrity, acrosomal status and DNA integrity before and after cryopreservation. With both techniques, there were similar post-thaw/warming results (P > 0.05) with respect to progressive motility, kinetic variables VCL, VSL, VAP and BCF, DNA fragmentation, sperm membrane functionality and morphological abnormalities. Total motile sperm, progression ratios LIN, STR, and WOB, the ALH, sperm viability and sperm with intact membrane and acrosome were greater (P < 0.05) in the conventional frozen-thawed sperm than vitrified-warmed sperm. Plasma testosterone concentrations varied from 0.0 ng/mL to 7.7 ng/mL. For epididymal sperm, sperm motility and viability following thawing were greater in vitrified-warmed samples than conventionally-frozen samples; however, small sample numbers precluded statistical analysis. When considered together, these results indicate vitrification may be a possible alternative for wolf sperm cryopreservation.

Cryopreservation of dog epididymal spermatozoa by conventional freezing or ultra-rapid freezing with nonpermeable cryoprotectant

This study was aimed to assess the effectiveness of two methods for cryopreservation of dog epididymal spermatozoa, one by conventional freezing (CF) with shortening both equilibration and cooling times, and the other by ultra-rapid freezing (URF) with nonpermeable cryoprotectant. Sixty epididymides were recovered from thirty orchiectomized adult dogs and the sperm samples were retrieved by retrograde flushing using TCG-EY (tris, citric acid, glucose + 20% egg yolk) extender and then 20 pools were conformed. Each pool was divided into 2 aliquots and then cryopreserved by CF and URF methods respectively. The CF method maintained the cooled-pool samples for 2h (1h without and 1h with 5% glycerol) and then were frozen by liquid nitrogen (LN₂) vapors for 2 min. The URF method cryopreserved the cooled-pool samples using TCG-EY+250 mM sucrose, equilibrating during 30 min (5 °C) and submerging 30-μL drops directly in LN₂. The results showed that the URF method produced a lower percentage of total and progressive motilities and acrosome integrity (P < 0.05) than the CF method. However, the kinetic variables (curvilinear and straight-line velocities, straightness, linearity, wobble, amplitude of lateral head displacement, and beat-cross frequency) and plasma membrane integrity did not differ (P > 0.05) between both cryopreservation methods. Unlike the URF method, the width, area and perimeter of sperm head were reduced after the CF method (P < 0.05). In conclusion, despite the low motility achieved after the ultra-rapid freezing method, the similar values of kinetic, viability and head morphometric dimensions to those obtained after conventional freezing, suggest that ultra-rapid freezing with sucrose may be a useful alternative for the cryopreservation of canine epididymal sperm.

Osmotic tolerance of rabbit spermatozoa is affected by extender composition and temperature

Sperm osmotic adaptability to anisosmotic conditions is important for sperm epididymal maturation, motility activation at ejaculation, and female tract colonization, or for conducting technological procedures such as cryopreservation. Several factors affect this adaptability, including the fluid composition that contributes to water flow dynamics, and the temperature at which osmotic stress is initiated. This study was designed to investigate the effect of medium composition (electrolyte- or sugar-based extender) and temperature (25 and 5 °C) on rabbit sperm adaptability to anisosmotic conditions. Rabbit spermatozoa, therefore, were diluted at both temperatures (25 and 5 °C) in electrolyte- or sugar-based media at increasing osmotic conditions (100 to 1,000 mOsm/kg), and values for sperm variables (sperm kinetics, membrane integrity, mitochondrial membrane potential) were estimated as endpoints. Sperm kinetics seemed to be more sensitive to osmotic stress than membrane integrity or mitochondrial function. The effect of moderate hypoosmotic stress did not differ when there was use of sugar- and electrolyte-based extenders at 25 °C (P > 0.05). In hyper-tonic conditions at 25 °C, the sugar-based extender was more effective in protecting sperm membrane integrity and mitochondrial function (P < 0.05). The lesser temperature made the differences more relevant because of the detrimental effect of hyperosmotic stress was more evident in the electrolyte-based extender at 5 °C (P < 0.05). The results from this study indicated rabbit spermatozoa have different adaptability to anisosmotic conditions induced by sugar- and electrolyte-based media and that the temperature at which the osmotic stress is initiated affects the cellular response.

First pregnancies in jennies with vitrified donkey semen using a new warming method

Sperm vitrification has been recently developed, but fertility trials have not been performed yet in equine species. In this study, a new warming technique for vitrified donkey semen was developed and the uterine inflammatory response and fertility were compared to conventional freezing. In Experiment 1, sperm was vitrified in straws and warmed in 3 ml of extender or in a water bath at: 37 °C/30 s; 43 °C/10 s; and 60 °C/5 s. Sperm motility, plasma and acrosome membranes and DNA integrity were compared between treatments. In Experiment 2, jennies were inseminated twice (500 × 10⁶ sperm) in the uterine body either with vitrified or frozen semen (2 cycles/jenny). Pregnancy rates and the uterine inflammatory response (polymorphonuclear neutrophil concentration; PMN) were evaluated after artificial insemination (AI). No differences between warming in extender/water bath were found and 43 °C/10 s was better than lower temperatures in terms of total (53.8 ± 13.2%) and progressive sperm motility (41.4 ± 11.4%). No differences in PMN concentration (×10³ PMN/ml) were found between vitrified (276.8 ± 171.6) or frozen (309.7 ± 250.7) semen after AI. However, PMN decreased faster (P < 0.05) using vitrified semen. Pregnancy rates were greater for vitrified (22%) than frozen semen (10%) but not statistically different. In conclusion, donkey sperm vitrified in straws could be directly warmed in a water bath at 43 °C/10 s, reducing the uterine inflammatory response obtained after AI and promoting positive pregnancy outcomes. These findings confirm the possibility to use vitrified semen as an alternative for AI in jennies.

The effect of cysteine and glutamine on human sperm functional parameters during vitrification

Assuming the adverse effects of reactive oxygen species (ROS) on sperm function, this study was conducted to assess the effects of cysteine and glutamine as effective antioxidants on human sperm parameters under vitrification. Twenty normozoospermic samples were used. The samples were subjected to a vitrification process and cysteine (5 and 10 mM) and glutamine (10 and 15 mM). The sperm motility parameters, mitochondrial membrane potential (MMP), plasma membrane integrity (PMI), DNA damage and intracellular ROS damage were assessed for each sample. Statistical analyses showed that motility, mitochondrial membrane potential and DNA damage decreased in the vitrified groups with cysteine 5, 10 mM and glutamine 10, 15 mM separately. Also intracellular ROS increased significantly compared to the fresh group (p < .05). No significant differences were observed for PMI compared with the fresh group (p > .05). Supplementation of cysteine and glutamine in both concentrations separately decreased intracellular ROS and DNA damage of spermatozoa with significant increase in PMI, MMP and progressive motility compared to vitrified control group (p < .05). The results showed no significant effect of a specific concentration in cysteine and glutamine on sperm parameters compared to other concentrations. Both amino acids have the potential to improve the harmful effects of freezing on sperm parameters.

Vitrification of donkey sperm using straws as an alternative to conventional slow freezing

Cryoprotectant-free vitrification of donkey sperm using 0.25 ml straws has been recently developed, but the obtained results have not been directly compared to conventional slow freezing yet. The aim of this study was to compare sperm quality parameters after cryopreservation using both methods. Semen samples were collected from three Andalusian Donkeys. Semen was centrifuged and pellets resuspended with an extender with glycerol for conventional freezing or the same extender without glycerol, but with sucrose 0.1 mol/L for vitrification. Conventional freezing was performed in nitrogen vapours and thawed in a water bath (30s/37°C). Vitrification was performed in covered 0.25 ml straws plunged directly into liquid nitrogen and warmed in 3 ml of a milk-based extender at 43°C. Total (TM, %) and progressive motility (PM, %) were evaluated by computer-assisted sperm analysis, and plasma membrane (PMI, %) and acrosome (AIS, %) integrities by epifluorescence microscopy. No differences (p > .05) were found between slow freezing and vitrification methods for any of the parameters assessed: TM (58.2 ± 16.1% vs. 52.7 ± 15.6%), PM (44.7 ± 18.2% vs. 44.3 ± 15.0%), PMI (55.4 ± 9.0% vs. 49.2 ± 11.2%) and AIS (38.4 ± 19.6% vs. 45.0 ± 11.0%), respectively. In conclusion, donkey sperm vitrification in straws presented similar sperm quality after thawing in comparison to conventional freezing. Therefore, it could be considered as an alternative to slow freezing regarding the sperm parameters assessed.

Vitrification of Donkey Sperm: Is It Better Using Permeable Cryoprotectants?

Simple Summary

Conventional donkey sperm-freezing using permeable cryoprotectants has been successfully performed, and good sperm parameters have been obtained after thawing. Unfortunately, artificial insemination of jennies with cryopreserved semen has given unsatisfactory results. Vitrification by directly dropping the sperm into the liquid nitrogen following the spheres methodology has been developed in human beings as an alternative to conventional freezing. This technique has shown to be a species-specific methodology and the concentration of cryoprotectants should be optimized in donkeys. Additionally, in this study, a permeable cryoprotectant (glycerol) has been tested for the first time for donkey sperm vitrification. According to our findings, vitrification of donkey sperm was effectively carried out using an extender supplemented with sucrose or bovine serum albumin (BSA) as non-permeable agent. When glycerol, a permeable agent, was compared to sucrose 0.1 M and BSA 5%, sperm quality significantly decreased. Therefore, donkey sperm vitrification in the absence of permeable agents obtained better results and gives a new approach to create a pattern for future studies of fertility trials.

Abstract

Vitrification by direct exposure of sperm to liquid nitrogen is increasing in popularity as an alternative to conventional freezing. In this study, the effect of permeable cryoprotectant agents for donkey sperm vitrification was compared to an extender containing non-permeable cryoprotectants. First, three different concentrations of sucrose (0.1, 0.2, and 0.3 molar, M) and bovine serum albumin, BSA (1, 5, and 10%) were compared. Secondly, the concentration of non-permeable agents producing the most desirable results was compared to an extender containing glycerol as permeable agent. Vitrification was performed by dropping 30 μL of sperm suspension directly into LN2 and warming at 42 °C. Sperm motility (total, TM; and progressive, PM) and plasma membrane integrity, PMI (mean ± SEM) were statistically compared between treatments. Sucrose 0.1 M showed a significantly higher percentage of total sperm motility (21.67 ± 9.22%) than sucrose 0.2 M (14.16 ± 4.50%) and 0.3 M (8.58 ± 6.22%); and no differences were found in comparison to the control (19.71 ± 10.16%). Vitrification with sucrose 0.1 M or BSA 5% obtained similar results for TM (21.67 ± 9.22% vs. 19.93 ± 9.93%), PM (13.42 ± 6.85% vs. 12.54 ± 6.37%) and PMI (40.90 ± 13.51% vs. 37.09 ± 14.28); but both showed higher percentages than glycerol (TM = 9.71 ± 4.19%; PM = 5.47 ± 3.17%; PMI = 28.48 ± 15.55%). In conclusion, donkey sperm vitrification in spheres using non-permeable cryoprotectants exhibited better sperm motility and viability parameters after warming than sperm vitrification using extenders containing permeable cryoprotectants.

Vitrification Using Soy Lecithin and Sucrose: A New Way to Store the Sperm for the Preservation of Canine Reproductive Function

A challenge in freezing semen for short and long-term availability is avoiding damage to intact spermatozoa caused by the freezing process. Vitrification protocols provide better results through less manipulation of semen and shorter freezing time compared to slow freezing techniques. Our research was aimed at improving vitrification methods for canine semen. Semen quality was determined in 20 ejaculates after collection. Each ejaculate was divided into eight aliquots, each with a different extender. The control extender contained TRIS, citric acid, fructose, and antibiotics. Soy lecithin and sucrose were added to the control extender at different concentrations to make up the test extenders and final concentration of 50 × 10⁶ spermatozoa/mL. From each group, a 33µL (1.65 × 10⁶ spermatozoa) suspension of spermatozoa was dropped directly into liquid nitrogen and devitrified at least one week later and evaluated as before. Soy lecithin at 1% and 0.25 M sucrose added to the base vitrification media effectively preserved all sperm qualities. Our results demonstrate the effectiveness of our methods. Vitrification media containing sucrose and soy lecithin cause a minimal decline in quality of canine semen after devitrification. Furthermore, extenders used in our research did not contain egg yolk, which was replaced by soy lecithin, thus allowing for ease of shipping to other countries with strict requirements.

Cryopreservation effects on canine sperm morphometric variables and ultrastructure: Comparison between vitrification and conventional freezing

Semen cryopreservation is an increasingly demanded technique in canids, particularly in order to preserve and spread high genetic value material. Sperm vitrification may represent an interesting alternative to costly and time consuming conventional freezing. The objective of this study was to evaluate the effect of sperm vitrification on sperm morphometry and ultrastructure compared to conventional freezing. Pools of nine beagle dogs were both frozen and vitrified. Computerized morphological parameters (length, wide, area and perimeter) and sperm ultrastructure, using scanning and transmission microscopy, were analysed in both fresh and in thawed/warmed samples. There were no differences (p > 0.05) between post-thaw and fresh morphometric variables of the sperm heads. However, cluster analysis revealed that sperm-heads turned out to be smaller after thawing (p < 0.05) in two of the four subpopulations. Vitrification-warming process led to an overall increase in sperm-head size. Furthermore, the sperm head size increased after warming in two subpopulations (p < 0.05). In conclusion, the variations in the sperm head area depended on the cryopreservation procedure (conventional freezing or vitrification). Conventional freezing tended to decrease the head dimensions, at least in some subpopulations, and vitrification led to an overall increase in the sperm head size. Decondensation of chromatin and plasma membrane blebbing in the head region was observed by transmission electron microscopy in several vitrified sperm, which might explain the increase of head dimensions detected by CASA-Morph system.

Knockout serum replacement is an efficient serum substitute for cryopreservation of human spermatozoa

The freeze-thaw procedure causes irreversible structural and functional changes in human spermatozoa. In order to decrease the detrimental effects of cryopreservation and improve the quality of post-thawed spermatozoa, the constituents of the freezing solution attracted considerable attention. In this study, for the first time, we evaluated the efficacy of knockout serum replacement (KSR) as a substitute for human serum albumin (HSA) for cryopreservation of human spermatozoa. Twenty semen samples were collected from normozoospermic men and divided them into five equal groups. One of the aliquots was diluted with glycerol-based medium as a control group (CON). The other four aliquots were diluted with the sucrose solution containing 5% HSA (H5), 10% HSA (H10), 5% KSR (K5), and 10% KSR (K10). The diluted samples were frozen and preserved in liquid nitrogen. Post thawed sperm parameters including motion characteristics, viability, membrane integrity, mitochondrial activity, acrosome integrity and DNA intactness in all of the sucrose-based groups were comparable with glycerol-based medium. The replacement of HSA by 10% KSR in the freezing medium resulted in significantly higher post-thawed viability, acrosome integrity and DNA intactness compared with other sucrose-based groups. In conclusion, the addition of 10% KSR to the sucrose-based freezing solution improves the quality of post-thawed human spermatozoa and may have potential to develop chemically defined freezing medium.

Ultra-rapid cooling of ibex sperm by spheres method does not induce a vitreous extracellular state and increases the membrane damages

Sperm cryopreservation by ultra-rapid cooling based on dropping small volumes of sperm suspension directly into liquid nitrogen, has been successful in some wild ruminant species, including the Iberian ibex (Capra pyrenaica). In ultra-rapid cooling, the contents of these droplets are expected to enter a stable, glass-like state, but to the best of our knowledge no information exists regarding the presence or absence of ice formation in the extracellular milieu when using this technique. Different modifications to the extracellular milieu likely inflict different types of damage on the plasmalemma, the acrosome and mitochondrial membranes. The aims of the present work were: 1) to examine the physical state of the extracellular milieu after cryopreservation at slow and ultra-rapid cooling rates—and thus determine whether ultra-rapid cooling vitrifies the extracellular milieu; and 2) to compare, using conventional sperm analysis techniques and scanning and transmission electron microscopy, the damage to sperm caused by these two methods. Sperm samples were obtained by the transrectal ultrasound-guided massage method (TUMASG) from anesthetized Iberian ibexes, and cryopreserved using slow and ultra-rapid cooling techniques. Sperm motility (22.95 ± 3.22% vs 4.42 ± 0.86%), viability (25.64 ± 3.71% vs 12.8 ± 2.50%), acrosome integrity (41.45± 3.73% vs 27.00 ± 1.84%) and mitochondrial membrane integrity (16.52 ± 3.75% vs 4.00 ± 0.65%) were better after slow cooling (P<0.001) than after ultra-rapid technique. Cryo-scanning electron microscopy (Cryo-SEM) suggested that the vitrified state was not achieved by ultra-rapid cooling, and that the ice crystals formed were smaller and had more stretchmarks (P<0.001) than after slow cooling. Scanning electron microscopy revealed no differences in the types of damage caused by the examined techniques, although transmission electron microscopy showed the damage to the plasmalemma and mitochondrial membrane to be worse after ultra-rapid cooling. In conclusion ultra-rapid cooling provoked more membrane damage than slow cooling, perhaps due to the extracellular ice crystals formed.

Ejaculated compared with epididymal stallion sperm vitrification

The aim of this study was to evaluate the effect of trehalose and lactose extenders on ejaculated and epididymal stallion sperm vitrification. Ejaculated semen samples were collected from seven fertile stallions, and cauda epididymis samples were collected from ten stallion carcasses after slaughter. Both the ejaculated and the epididymis samples were diluted and vitrified using INRA 96® and bovine serum albumin as well as trehalose or lactose. As a control, ejaculated and epididymal samples were collected and frozen using the conventional method. Vitrification was performed by immersing sperm suspensions directly in LN2. After thawing or devitrification, there was assessment of samples for sperm motility using computer-assisted analysis. Viability was assessed using SYBR-14 and propidium iodide (PI) and acrosome integrity by fluorescein using isothiocyanate combined with peanut agglutinin (FITC-PNA) and PI. Epididymal sperm vitrification with trehalose (EPT) or lactose (EPL) resulted in greater progressive sperm motility than sperm of the control sample (EPC). After post-thaw/devitrification of sperm in the EPT group, sperm motility was greater (P<0.001) compared to that using EPL (50.72 ± 5.09% compared with 34.21 ± 3.02%). The results from assessment of ejaculated sperm samples after undergoing the vitrification process indicated cells were less viable (P<0.001) than the control (EJC) sample. In conclusion, vitrification of epididymal stallion sperm using trehalose might be a beneficial alternative for the long-term storage of sperm samples with great economic value. Spermatozoa from vitrified ejaculates of stallions, however, had lesser motility and viability rates than samples subjected to conventional freezing.

A simple method of human sperm vitrification

Human sperm vitrification is a novel method of sperm freezing which achieves cryopreservation due to ultra-rapid cooling rates that prevent ice-crystal formation. However, sperm vitrification protocols are still largely not standardized for routine clinical use and seldom achieve a post warm sperm survival of 25-35%. The study aim was to validate and optimize a simple method of sperm vitrification that yields a high survival rate of spermatozoa for clinical use. Semen samples from 10 normozoospermic patients were subject to a simple swim-up into pre-warmed gamete handling media. Swim-up specimens were mixed in a 1:1 ratio with 0.5 M sucrose. Swim up specimens were then directly dropped in liquid N2. After a week of storage samples where warmed at 42 degree Celsius and sperm motility and viability was estimated. The mean sperm total motility of the fresh sample after the swim up preparation was 94.3 ± 3.06 %. Upon, vitrification followed by warming the mean percentage of total motile sperm fraction recovered was 74.70 ± 5.60 %. The mean sperm progressive motility of vitrified-warmed spermatozoa was 68 ± 8.47 %. The overall mean percentage of motile sperm recovery was 70.05% of the fresh swim up sample in this study. The overall mean sperm viability as assessed using the HOST vitality test was 77.21 ± 7.52%. •This study presents a simple protocol on the 'droplet method' of sperm vitrification.•Sperm cells vitrified using our modified method show a >70% motility and viability rates compared to the routine 25% to 35% of reported survival with the original sperm vitrification/freezing methodologies. This survival is attributed to a crucial change in the warming step.•This method has the advantage of using no toxic cell permeating cryoprotectant or expensive programmable freezing devices.

Strategies to Minimize Various Stress-Related Freeze-Thaw Damages During Conventional Cryopreservation of Mammalian Spermatozoa

The aim of the article is to report a review on different sperm cryopreservation techniques, various stress-related freeze-thaw damages altering sperm structure and function during conventional cryopreservation, and strategies to minimize these stresses. Sperm cryopreservation has allowed indefinite storage and successful transportation of valuable germplasm from proven sites at distant locations, for genetic upgradation through implementation of reproductive techniques, such as artificial insemination. Different techniques for sperm cryopreservation have been proposed such as conventional freezing techniques, directional freezing, and sperm vitrification. Drawbacks related to conventional freezing methods, such as heterogeneous ice nucleation and repeated freeze-thaw cycles at the ice front that disrupts and kill sperm cells, led to the emergence of the directional freezing technique. Sperm vitrification is advantageous as there is no ice crystal-induced physical damages to sperm. However, sperm vitrification has less applicability as encouraging results are only reported in human, dog, and cat. In spite of several drawbacks, conventional freezing techniques are still most widely used for sperm cryopreservation. Spermatozoa experience stresses in the form of cold shock, osmotic stress, and mainly oxidative stress during conventional cryopreservation ultimately reduces the sperm viability and fertility. Several attempts have been made in the past to minimize all these stresses individually or in combination. Membrane fluidity was increased to prevent the cold shock and cryocapacitation-like changes by the addition of cholesterol to the membrane. Antifreeze proteins were added in semen extender to minimize freeze-thaw damages due to heterogeneous ice nucleation and ice recrystallization. Oxidative stress was reduced either by neutralizing reactive oxygen species (ROS) through enzymatic, nonenzymatic, plant-based antioxidants or reductants; or by minimizing the level of sources like the semen radiation exposure, leucocytes, and dead and defective spermatozoa, which lead to ROS production during the semen cryopreservation process. A novel approach of minimizing oxidative stress was to reduce the oxygen tension in sperm microenvironment that is, extender by partial deoxygenation process, as a number of literatures pointed out direct link of O₂ with ROS production. When compared with other strategies, partial deoxygenation of semen extender with N₂ gassing is found as a cost-effective, comparatively easy and a potential approach to large-scale frozen semen production.

The anti-oxidant roles of Taurine and Hypotaurine on acrosome integrity, HBA and HSPA2 of the human sperm during vitrification and post warming in two different temperature

Despite advances in vitrification techniques for sperm cryopreservation, cryo-damages of sperm caused by generation of reactive oxygen species (ROS) continue to impede implementation of this technique. This study analyses the effects of taurine and hypotaurine as anti-oxidants during vitrification of human sperms. The study was performed in two steps. In the first step, 20 normospermic semen samples were vitrified in the presence of varying concentrations of taurine and hypotaurine, and their effects as anti-oxidant agents on classical sperm parameters, hyaluronan-binding assay (HBA), lipid peroxidation (LPO) and acrosome reaction (AR) were studied. Statistical analyses showed that the sperm parameters in all vitrified groups decreased significantly (P < 0.05) compared to the fresh group. However, HBA and acrosome integrity in vitrified groups containing taurine and 50 mM of hypotaurine were better than in the control group (P < 0.05). The morphology of the vitrified group was good only in the group that contained 50 mM of hypotaurine (P < 0.05). Based on the results from the first step, 50 mM of hypotaurine was considered the ideal anti-oxidant formulation and further tests were carried out on 10 normospermic semen samples with this protecting agent. In addition to the mentioned parameters, the expression of heat shock proteinA2 (HSPA2) was studied in the vitrified group with 50 mM hypotaurine, warmed under two different warming temperatures 37 and 42 °C. 50 mM Hypotaurine was found to equally improve motility, morphology, HBA, and AR after warming at 37 °C and 42 °C (P < 0.05). However, at both warming temperatures, the expression of HSPA2 was reduced in all vitrified groups comparing to the fresh group (P < 0.05). In conclusion, taurine and hypotaurine antioxidants, especially 50 mM hypotaurine, are able to reduce deleterious cryo-injuries on morphology, acrosome and HBA and improve sperm recovery at both warming temperatures (37 and 42 °C). However, they do not have any protective action on expression of HSPA2.

Improved cryopreservation of spermatozoa using vitrification: comparison of cryoprotectants and a novel device for long-term storage

STUDY QUESTION

Does cryoprotection of spermatozoa using a vitrification protocol with improved cryoprotective agents and a novel device for large storage lead to better outcomes than conventional slow freezing? Vitrification of human sperm using sucrose and dextran-based cryoprotectant (CPA4) with a new vitrification device resulted in significantly better sperm motility and progressive motility and improved DNA integrity with lower DNA fragmentation compared with conventional slow freezing.

WHAT IS KNOWN ALREADY

A major limitation to clinical implementation of vitrification is the right balance between the volume of spermatozoa suspension cryopreserved and a standardised use of CPAs for survival of spermatozoa.

STUDY DESIGN, SIZE, DURATION

This was a control versus current clinical practice study using 30 fresh human semen samples to carry out the different cryoprotectant analyses followed by a further 23 semen samples to test the novel vitrification protocol.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All human specimens fulfilled the following criteria: > 5 million spermatozoa/mL, > 20% total motility, ≥ 1.8 mL in volume, with all participants falling within the age range of 25-45 inclusively. The concentration, progressive motility, non-progressive motility, immotility, and various morphokinetic variables including DAP, DCL, DSL, LIN, and STR were then determined using the IVOS II™ Clinical CASA system (Hamilton Thorne, Beverly, MA, USA) on the basis of the 5th Edition of WHO Laboratory Manual for the Examination and Processing of Human Semen.

MAIN RESULTS AND THE ROLE OF CHANCE

Among the 6 cryopreservation methods in this study, vitrification with the funnel-shaped device using CPA4 best preserves the 13 sperm parameters evaluated by CASA system. Conventional slow freezing and vitrification with the device using seminal plasma also protects sperm quality, but the overall motilities are statistically lower in comparison with the novel vitrification approach with cryoprotective media using the device. DNA fragmentation significantly increased after cryopreservation through the method of conventional slow freezing (p = 0.07). There was no significant difference in DNA fragmentation between fresh control and vitrification (p = 1.000).

LIMITATIONS, REASONS FOR CAUTION

Extensive training is required to minimise the human error in using the vitrification device to perform cryopreservation. Each operator can only handle one sample at a time with device vitrification, whereas several samples can be processed without the need for special training with conventional slow freezing.

WIDER IMPLICATIONS OF THE FINDINGS

The presented study shows that a new vitrification method could improve survival sperm rate. Human sperm vitrification using our novel protocol gives higher motility and progression and lower percentage of DNA fragmentation than conventional slow freezing. Our findings indicate that this method could supersede the current clinical practice in particular for patients with oligospermia as it reduces osmotic damage, time, and cost.

Vitrification of stallion sperm using 0.25 ml straws: Effect of volume, concentration and carbohydrates (sucrose/trehalose/raffinose)

Sperm vitrification is a rapid freezing method in which carbohydrates are used as cryoprotectants. The aim of this study was to determine the optimal volume, concentration and type of carbohydrates for stallion sperm vitrification using 0.25 ml straws in comparison to conventional freezing. Ejaculates (n = 54) were collected from six stallions. For vitrification, straws were filled with different volumes (30, 70, 100 μl), sperm concentrations (50, 100, 200 × 10⁶ sperm/ml) and extenders containing sucrose (20, 100, 200 mM), trehalose (50, 100, 200 mM) and raffinose (50, 100, 200 mM) and plunged into LN₂. Conventional freezing was performed in 0.5 ml straws frozen in LN₂ vapors. Sperm motility, plasma and acrosome membrane integrities and DNA fragmentation were compared among treatments. The use of straws filled with 100 μl at 100 × 10⁶ sperm/ml with the extender containing 100 mM trehalose resulted in greater values for sperm quality than the other concentrations, volumes and carbohydrates. With vitrification, there were greater values (mean ± SEM; P < 0.05) than freezing for progressive motility (48.2 ± 2.3 compared with 37.3 ± 2.2%), plasma membrane integrity (82.8 ± 1.5 compared with 74.1 ± 1.9%), and intact acrosomes (50.2 ±  1.2 compared with 43.1 ± 1.4%); and less DNA fragmentation (6.4 ± 0.7 compared with 8.2 ± 0.3%). In conclusion, stallion sperm can be vitrified in 0.25 ml straws filled with 100 μl of sperm at 100 x 10⁶ sperm/ml using an extender with 100 mM of trehalose, obtaining better sperm quality after warming than conventional freezing.

Optimization of donkey sperm vitrification: Effect of sucrose, sperm concentration, volume and package (0.25 and 0.5 mL straws)

The aim of this study was to assess the effect of different factors affecting vitrification success of donkey sperm: extender, sperm concentration, volume and storage vessel type. In Experiment 1, sucrose supplementations at 0.25 and 0.1 M were compared using two base extenders (containing or not egg-yolk); in Experiment 2, three sperm concentrations were assessed: 100, 200 or 300 million sperm/mL; and in Experiment 3, three different sperm volumes (100, 160 and 200 μL) and two different storage vessels (0.25 and 0.5 mL straws) were assessed. Sperm motility variables (CASA), plasma membrane and acrosome (evaluated under fluorescence microscopy) and sperm DNA integrity (flow cytometry) were evaluated after warming with comparisons of protocols. There was a greater total (55.7 ± 16.4%) and progressive (44.0 ± 11.5%) motility using the extender with egg-yolk and 0.1 M sucrose. There were no effects of sperm concentrations on vitrification results (P > 0.05). The 0.25 mL covered straw showed higher values than the 0.5 mL straw for total (50.0 ± 17.3% vs 2.0 ± 6.7%) and progressive (40.5 ± 14.9% vs 0.9 ± 1.5%) motility, plasma membrane (43.9 ± 14.4% vs 14.0 ± 16.4%) and acrosome integrity (51.5 ± 13.6% vs 28.0 ± 14.7%), respectively. In conclusion, values for donkey sperm quality variables after vitrification were greater using an extender containing egg-yolk and 0.1 M sucrose, at 300 million sperm/mL in 0.25 mL straws with outer covers.

Recent advances in bovine sperm cryopreservation techniques with a focus on sperm post-thaw quality optimization

Sperm cryopreservation facilitates the storage and transport of germplasm for its use in artificial insemination (AI) and other advanced reproductive technologies. The cryopreservation process can damage sperm and compromise functionality. Several cryobiological studies have found that the physical and biological factors that affect sperm survival at low temperatures during the cryopreservation process often involve the integrity of sperm membrane. In this review, the behaviour of the sperm membrane against cooling, cold shock, ice crystal formation, oxidative stress, osmotic changes, reorganization of the lipid bilayer and addition of cryoprotective agents (CPA) is discussed. In addition, the phenomenon of reactive oxygen species (ROS) and its relationship with the cryopreservation process is also described. Semen cryopreservation techniques have progressed slowly in past years, and the current performance, measured as post-thawed survival, is not very different compared to past decades. Recent advances in understanding the structure of the cell membrane, its function and metabolism have driven to new conservation systems, including lyophilization and vitrification. However, none of these technologies is commercially available, although its future appears very promising.

Vitrification in straws conserves motility features better than spheres in donkey sperm

Sperm vitrification as alternative to conventional freezing is increasing in popularity in many species. It has been achieved by direct exposure of diluted semen to liquid nitrogen in spheres or straws. Both techniques have been successfully developed, but they had not been compared yet in donkeys. The aim of this study was to compare these two methods of vitrification for donkey semen. Ejaculates from six Andalusian donkeys were collected and extended in Gent without glycerol supplemented with sucrose 0.1 M (Molar). Samples were slowly cooled at 5°C. For vitrification, 30 μl suspensions (spheres) were dropped directly into liquid nitrogen (LN₂ ) or filled in covered 0.25 ml straws and then plunged into the LN₂ (straws). For warming, straws and spheres were directly immersed in 3 ml of INRA-96 at 43°C. Total (TM, %) and progressive motility (PM, %) were objectively evaluated by computer-assisted sperm analysis and plasma membrane integrity (PMI, %) by epifluorescence microscopy. Results showed the straw method resulted in significantly higher values than spheres for: TM (54.7% ± 10.1 vs. 28.6% ± 6.5) and PM (44.2% ± 9.4 vs. 17.7% ± 6.4), but no significant differences were found between straws or spheres for PMI (31.5 ± 10.7 vs. 41.6 ± 14.3) respectively. In conclusion, donkey sperm could be vitrified in straws obtaining better sperm motility parameters after warming in comparison to the sphere method.

Freezing, Vitrification, and Freeze-Drying of Equine Spermatozoa: Impact on Mitochondrial Membrane Potential, Lipid Peroxidation, and DNA Integrity

Maintaining the integrity of equine sperm subjected to preservation protocols is essential for the successful development of assisted reproduction procedures. The aim of this study was to assess the mitochondrial membrane potential, lipid peroxidation, and DNA integrity of equine sperm subjected to freezing, vitrification, and freeze-drying. Eight ejaculates obtained from four Colombian Creole horses were subjected to programmable freezing, vitrification, and freeze-drying. After thawing or rehydration, sperm motility and kinetics were assessed through a CASA system. The mitochondrial membrane potential (ΔΨM), lipid peroxidation (LPO), and DNA fragmentation index (DFI) of the spermatozoa were assessed by flow cytometry using the DiOC6 (3), C11-Bodipy 581/591, and propidium iodide (PI) fluorescent dyes. The statistical analysis was conducted via generalized linear models, mean comparisons via the Duncan test, and a principal component analysis. A higher rate of spermatozoa with a high ΔΨM was found for freeze-drying (40.26 ± 7.79%) compared with freezing (21.82 ± 5.38%) and vitrification (5.32 ± 1.17%) (P < .05). Likewise, a higher rate of nonperoxidized viable spermatozoa (Bodipy-/PI-) was found for freeze-drying (35.98 ± 7.01%) in relation to frozen (10.34 ± 2.69%) and vitrified (7.07 ± 2.00%) sperm (P < .05). The DFI of vitrified spermatozoa (0.12 ± 0.04%) was higher when compared with the frozen (0.03 ± 0.01%) and freeze-dried (0.02 ± 0.01%) samples (P < .05). The researchers conclude that vitrification generates greater sperm alterations than freeze-drying and freezing, whereas freeze-drying produces lower LPO and higher ΔΨM for equine spermatozoa.

Modern human sperm freezing: Effect on DNA, chromatin and acrosome integrity

OBJECTIVE

Presence of vitrification method in sperm freezing and the introduction of solid surface vitrification beside rapid freezing in vapour, opens an easy and safe way to help infertility centres. While the effects of cryopreservation on motility, morphology and viability of sperm are documented, the question of the probable alteration of sperm DNA, chromatin and acrosome integrity after freezing and thawing procedures in different methods is still controversial.

MATERIALS AND METHODS

Normal sample were collected according to WHO strict criteria. Sperm suspensions were mixed 1:1 with 0.5 M sucrose and divided into four equal aliquots for freezing: fresh, nitrogen direct immersion vitrification (Vit), solid surface vitrification (SSV) and in vapour (Vapour). Sperm suspensions were transferred into a 0.25 ml sterile plastic. Then straw was inserted inside the 0.5 ml straw. For thawing, the straws were immersed in a 42 °C water bath. Beside the sperm parameters, we assessed the acrosome reaction by double staining, chromatin integrity by toluidine blue (Tb) and chromomycin A3 (CMA3) and DNA integrity by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) respectively.

RESULTS

In progressive motility, the highest rate occurred in Vit (39.9 ± 13.3). Moreover, the lowest rate of immotile sperm was in Vit (32.7 ± 16.3). In normal morphology, the group Vit was similar to the fresh, while SSV and Vapour were significantly different from the fresh. The percentage of acrosome-reacted sperms was more in Vit (81.3 ± 10.2) than the fresh group. TUNEL+ results showed that DNA fragmentation was significantly increased in Vit (p-value = 0.025). While in SSV and Vapour results were comparable to fresh. There was a significant correlation between TUNEL+ and normal morphology, TB, CMA3 and presence of intact acrosome.

CONCLUSION

Sperm in Vapour was healthier in terms of DNA, chromatin and acrosome integrity. In contrast of higher motility and normal morphology; DNA, chromatin and acrosome integrity were decreased in Vit. However, these findings were more acceptable in SSV or Vapour.

Reproduction biotechnologies in germplasm banking of livestock species: a review

Many biotechnologies are currently used in livestock breeding with the aim of improving reproductive efficiency and increasing the rate of genetic progress in production animals. Semen cryopreservation is the most widely used cryobiotechnology, although vitrification techniques now allow embryos and oocytes to be banked in ever-increasing numbers. Cryopreservation of other types of germplasm (reproductive tissue in general) is also possible, although the techniques are still in the early stages of development for use in livestock species. Although still in their infancy, these techniques are increasingly being used in aquaculture. Germplasm conservation enables reproductive tissues from both animals and fish to be preserved to generate offspring in the future without having to maintain large numbers of living populations of these species. However, such measures need careful planning and coordination. This review explains why the preservation of genetic diversity is needed for livestock and fish, and describes some of the issues involved in germplasm banking. Furthermore, some recent developments in semen handling leading to improved semen cryopreservation and biosecurity measures are also discussed.