The effects of cooling rates and type of freezing extenders on cryosurvival of rat sperm

Association between different soy lecithin-based extenders and freezing rates in ram semen cryopreservation

The aim of the study was to evaluate the effect of the association between glycine-milk (GM) based extenders made with different concentrations of soy lecithin (SL) and freezing rates (FR) on semen quality after thawing. Pooled semen from rams (n = 12) were diluted in GM extenders with 20% egg yolk (EY-20%) or with different concentrations of SL: 0.5% (SL-0.5%), 1.0% (SL-1.0%), and 2.0% (SL-2.0%). The diluted semen (150 ×10⁶ spermatozoa/0.25 mL) was frozen at three FR of - 10, - 20, and - 60 °C/min, and subsequently thawed and analyzed. Results revealed that EY-20% and SL-2.0% had better kinetic parameters, and showed higher proportions of viable, non-apoptotic, plasma-membrane-intact spermatozoa (A^-/PI^-) and non-capacitated spermatozoa (F), and had lower acrosome-reacted spermatozoa (AR) in the EY-20% and satisfactory values for SL-2.0% compared to SL-0.5% and SL-1.0% (P < 0.05). The FR at - 20 and - 60 °C/min maintained higher A^-/PI^- and viable spermatozoa compared to - 10 °C/min. The combination EY-20% and - 60 °C/min showed the highest A^-/PI^- and F (P < 0.05) and the lowest AR, and it did not differ from the combinations EY-20% at - 20 °C/min and SL-2.0% at - 20 °C/min (P > 0.05). In conclusion, the combination EY-20% and - 60 °C/min, showed the best cryoprotective effects on ram spermatozoa. Changes in spermatozoa after thawing were related to the use of the type of extender, the amounts of the same compound in the extender, and the freezing rates to which they were subjected.

Effects of Antifreeze Protein Type I and Glycerol in Diluents on Cryopreserved Goat Epididymal Sperm

The effect of antifreeze protein (AFP) as a cryoprotectant used in different concentrations of glycerol on post-thaw quality of epididymal sperm was investigated. Sperm were isolated from 50 testicles, obtained from 25 healthy mature goat bucks, with progressive motility >80%, and total morphological abnormalities <10% were pooled in each replication. The semen samples were diluted with Tris-citrate-fructose-soybean lecithin extender containing different concentration of AFP [0 μg/mL (A0), 5 μg/mL (A5), 10 μg/mL (A10)]. Each concentration of AFP was added in an extender containing either 7% (G7) or 5% (G5) glycerol. Post-thaw total and progressive motility were found to be higher (p < 0.05) in groups A5G5 and A5G7. Plasma membrane integrity, sperm acrosome integrity, DNA integrity, acrosome intact sperm, and mitochondrial membrane potential were found to be higher (p < 0.05) in groups A5G5 and A10G5. Sperm viability was found to be higher (p < 0.05) in group A5G5, while lipid peroxidation was recorded lower (p < 0.05) in groups A5G5 and A5G7. Regarding the apoptosis occurrence, the results demonstrate higher (p < 0.05) live post-thawed spermatozoa for groups containing 5 μg/mL AFP with 5% and 7% glycerol in addition to the lowest (p < 0.05) value for groups containing 0 μg/mL AFP with 5% and 7% glycerol. Based on these results, the present study concludes that the addition of 5 μg/mL AFP in combination with 5% glycerol in freezing extender improves the post-thaw quality, structure, and function parameters for buck spermatozoa.

Effects of escitalopram treatment and chronic mild stress induced from peripuberty on spermatic parameters of adult rats

BACKGROUND

The prevalence of depression in adolescents has significantly increased worldwide. Escitalopram is a selective serotonin reuptake inhibitor approved for treatment of psychiatric disorders in children and adolescents by the Food and Drugs Administration.

AIMS

This study aimed to evaluate the sperm parameters of adult rats exposed to chronic mild stress (CMS), from peripuberty to adulthood, treated or not with escitalopram.

MATERIALS AND METHODS

Sixty-two male rats were distributed into four groups: S - submitted to CMS; E - Escitalopram (10 mg / kg, via gavage); ES - CMS + ES; SC - Sham control. The induced depression protocol consisted of the exposure of the animals to nine different stressors (one stressor/day), randomly for 8 weeks, from peripuberty (41 days postpartum, dpp) to adulthood (97 dpp). The escitalopram treatment period started at 70 dpp and lasted 4 weeks. The euthanasia was performed for biological material collection at 114 dpp. Morphometric, biometric, sperm parameters, oxidative stress analyses, and corticosterone dosage were carried out.

RESULTS

There was a reduction of the sperm daily production and sperm concentration in the epididymis of rats treated and/or submitted to CMS. These groups (E, S, ES) also showed reduction of the mitochondrial activity; acrosome integrity; sperm chromatin compaction; sperm motility and vitality, besides an increased frequency of morphologically abnormal sperm. The sperm transit time through the epididymis was significantly higher in the escitalopram-treated rats (E, ES). No differences were observed regarding the sperm DNA fragmentation. The lipid peroxidation was significantly increased at the epididymal (E, S, and ES group) and testicular levels (S group).

CONCLUSION

The CMS with or without escitalopram treatment altered the oxidative status in sperm and male organs, worsening the qualitative and quantitative sperm parameters, which can probably compromise the male fertility.

Implementation of a method for sperm cryopreservation in sceloporine lizards

Actual loss of lizard biodiversity continues, even with the implementation of conventional conservation programs. An approach including assisted reproductive techniques such as sperm cryopreservation may contribute to the management of endangered species. We developed a method for sperm cryopreservation in sceloporine lizards and compared the response among the studied species. Prior to the mating season, we obtained semen from adult males of Sceloporus aeneus (n = 21), Sceloporus grammicus (n = 20) and Sceloporus torquatus (n = 21) via pressure of the genital papilla. Volume and sperm concentration were measured before semen dilution in a Tris-egg yolk (TEY) medium to evaluate progressive motility, sperm viability, morphology, plasma membrane and acrosome integrity. Then, we cooled the remaining volumes to 5°C at a rate of 0.1°C per minute to incorporate glycerol (8% v/v) in two fractions. Immediately afterwards, we placed 40 μl of the mix on solid CO2 to form pellets and immersed them in liquid nitrogen for storage. We thawed the pellets at 29°C for 3 minutes and diluted them 1:1 (v/v) in TEY medium to assess sperm quality. We found a positive relationship between body weight and seminal volume in S. grammicus and S. torquatus and a negative correlation with sperm concentration in S. grammicus (P < 0.05). Moreover, we observed that the freezing-thawing process decreased sperm quality in the three species, mostly affecting motility and viability. However, S. torquatus and S. aeneus showed a higher sperm tolerance than S. grammicus.

Sodium dodecyl sulphate, N-octyl β-D glucopyranoside and 4-methoxy phenyl β-D glucopyranoside effect on post-thaw sperm motion and viability traits of Murrah buffalo (Bubalus bubalis) bulls

Sodium Dodecyl Sulphate (SDS), N-Octyl β-D Glucopyranoside (NOG), 4-Methoxy Phenyl β-D Glucopyranoside (4-MPG) as ice recrystallization inhibitors were added to Tris Egg Yolk Glycerol (TEYG) semen extender for cryopreservation of semen of buffalo bulls. Post-thaw sperm motion and viability traits were evaluated. Pilot study involved six semen ejaculates (2 ejaculates/bull, from three bulls); second experiment was conducted using twenty seven semen ejaculates (9 ejaculates/bull, from 3 bulls) and in third experiment three semen ejaculates (one bull) were used. Eight concentrations of SDS (2, 1, 0.5, 0.25, 0.15, 0.125, 0.0625 and 0.0312%), twelve concentrations of NOG (33, 22, 11, 5.5, 2.5, 0.75, 0.5, 0.25, 0.125, 0.0625, 0.03125 and 0.0156 mM), and, eleven concentrations of 4-MPG (220, 165, 110, 55, 50, 25, 12.5, 6.25, 3.125, 1.56 and 0.78 mM) were supplemented in TEYG semen extender to evaluate the post-thaw sperm motility and viability traits. Computer Assisted Sperm Analysis (CASA) was used to measure the kinetic and functional parameters for sperm motion traits, Hypo Osmotic Swelling Test (HOST) for sperm plasma membrane integrity, Eosin Nigrosin staining for viability and Rose Bengal staining for sperm abnormalities for all the experiments except for pilot study where only Total Motility (TM) and Rapid Progressive Motility (RP) were evaluated. Three freezing protocols; i) Normal P24 (freezing rate of -30 °C min^-1 from 4 °C to -15 °C; -40 °C min^-1 from -15 °C to -60 °C; and -50 °C min^-1 from -60 °C to -140 °C; and then plunged in liquid Nitrogen at -196 °C); ii) Moderate P25 (freezing rate of -30 °C min^-1 from 4 °C to -15 °C; -50 °C min^-1 from -15 °C to -60 °C; and -50 °C min^-1 from -60 °C to -140 °C; and then plunged in liquid Nitrogen at -196 °C); and iii) Rapid P26 (freezing rate of -30 °C min^-1 from 4 °C to -15 °C; -60 °C min^-1 from -15 °C to -60 °C; and -50 °C min^-1 from -60 °C to -140 °C; and then plunged in liquid Nitrogen at -196 °C) were evaluated using SDS 0.125% in TEYG semen extender. SDS ≤0.125%, NOG ≤0.0625 mM and 4-MPG ≤ 3.125 mM in TEYG buffalo semen extender improved significantly (p < .05) the kinetic and functional parameters as compared to the other Ice Recrystallization Inhibitors (IRIs) concentrations used for cryopreservation of buffalo bull semen in the pilot study. SDS 0.125% supplementation was the best IRI among all which resulted in improved kinetic and functional parameters of bull semen in second experiment. Conclusion was drawn that buffalo bull semen cryopreservation using sodium dodecyl sulphate, 0.125% as IRI in TEYG semen extender along with freezing protocol P 25 revealed optimum kinetic and functional parameters for post-thaw spermatozoa.

Melatonin and selenium supplementation in extenders improves the post-thaw quality parameters of rat sperm

Objective

The aim of this study was to determine the effects of melatonin and selenium in freezing extenders on frozen-thawed rat sperm.

Methods

Semen samples were collected from 20 adult male Wistar albino rats. Following dilution, the samples were divided into six groups: four cryopreserved groups with 1 mM and 0.5 mM melatonin and selenium supplements, and two fresh and cryopreserved control groups. The rapid freezing technique was used to freeze the samples. Flow cytometry was used to assess plasma membrane integrity, mitochondrial membrane potential, and DNA damage, while computer-assisted sperm analysis was used to assess motility.

Results

Total motility was higher in the 1 mM melatonin supplementation group than in the cryopreserved control group (mean±standard error of the mean, 69.89±3.05 vs. 59.21±1.31; p≤0.05). The group with 1 mM selenium had the highest plasma membrane integrity (42.35%±1.01%). The cryopreserved group with 0.5 mM selenium had the highest mitochondrial membrane potential, whereas the cryopreserved control group had the lowest (45.92%±4.53% and 39.45%±3.52%, respectively).

Conclusion

Cryopreservation of rat semen supplemented with 1 mM melatonin increased sperm motility after freeze-thawing, while supplementation with 0.5 mM selenium increased mitochondrial activity.

Strategies for Highly Efficient Rabbit Sperm Cryopreservation

The rabbit is a valuable animal for both the economy and biomedical sciences. Sperm cryopreservation is one of the most efficient ways to preserve rabbit strains because it is easy to collect ejaculate repeatedly from a single male and inseminate artificially into multiple females. During the cooling, freezing and thawing process of sperms, the plasma membrane, cytoplasm and genome structures could be damaged by osmotic stress, cold shock, intracellular ice crystal formation, and excessive production of reactive oxygen species. In this review, we will discuss the progress made during the past years regarding efforts to minimize the cell damage in rabbit sperms, including freezing extender, cryoprotectants, supplements, and procedures.

Cryopreservation of Spix's yellow-toothed cavy epididymal sperm using Tris- and coconut water-based extenders supplemented with egg yolk or Aloe vera

Addressing the establishment of biobanks for the conservation of wild hystricomorph rodents' germplasm, we verified the effects of different extenders and distinct concentrations of non-permeant cryoprotectants on the sperm parameters of Spix's yellow-toothed cavies. Nine testis-epididymis complexes were used for sperm collection by retrograde washing using Tris or a powdered coconut water extender (ACP®-116c). Spermatozoa were diluted and frozen with the same extenders supplemented with egg yolk or Aloe vera at a 10% or 20% concentration. After recovery and cryopreservation, all samples were evaluated for sperm kinetic parameters, morphology, membrane integrity, osmotic response, and sperm-binding capability using an egg yolk perivitelline membrane assay. After recovery, no differences were observed between Tris and ACP®-116c that provided 515.4 × 10⁶ sperm/mL and 561.6 × 10⁶ sperm/mL, presenting >65% motile sperm, respectively. After cryopreservation, most effective preservation of sperm kinetic parameters (68.1 ± 5.9% motile sperm) and membrane integrity (48.2 ± 7.4%) was provided by Tris extender supplemented with 10% egg yolk. However, both extenders supplemented with any concentration of egg yolk or Aloe vera presented similar preservation of osmotic response and sperm-binding ability after cryopreservation. In summary, we suggest the use of a Tris extender supplemented of 10% egg yolk for cryopreservation of Spix's yellow-toothed cavy epidydimal sperm.

Influence of Different Combinations of Permeable and Nonpermeable Cryoprotectants on the Freezing Capacity of Equine Sperm

This study was aimed to evaluate the effect of permeable cryoprotectants in combination with trehalose or sucrose on the freezing capacity of stallion sperm. For this purpose, the ejaculates (n = 24) were collected from four healthy mature Turkmen stallions. The ejaculates were pooled and diluted with one of the extenders containing a combination of 5% of permeating (dimethylacetamide [DMA]; dimethylformamide [DMF] or glycerol) and 50 mM of nonpermeating cryoprotectant agents (CPAs) (sucrose or trehalose) to a final concentration of 200 × 10⁶ spermatozoa/mL. The extended samples were cryopreserved and thawed using a standard protocol. The samples were evaluated for motion kinetics, morphological abnormalities, plasma membrane functionality (PMF), viability, and lipid peroxidation. The results showed that the sperm cryopreserved in extender containing DMA produced higher (P ≤ .05) total motility, straightness, straight line velocity, curvilinear velocity, and lower (P ≤ .05) lipid peroxidation (malondialdehyde [MDA] concentration) compared with DMF and glycerol groups. Overall, both DMA and DMF have shown higher (P ≤ .05) sperm motion kinetics, viability, PMF, and lower (P ≤ .05) morphological abnormalities and MDA concentration compared with the glycerol. However, except morphological abnormalities, all of the other parameters did not differ between trehalose and sucrose. Likewise, there was no interaction between permeating and nonpermeating CPAs (P ≥ .05) except in terms of sperm abnormalities (P ≤ .05). In conclusion, the use of DMA or DMF as alternative CPAs of glycerol could be more effective for successful cryopreservation of stallion sperm. The nonsignificant interaction between permeating and nonpermeating CPAs for most of the post-thaw sperm parameters negates possible synergism among these compounds.

A new strategy and system for the ex vivo ovary perfusion and cryopreservation: An innovation

Children and young adults, who suffer from cancer, receive gonadotoxic therapy, which destroys their fertile abilities after survival. Ovarian cryopreservation and transplantation provide the promising solution to this problem, where the ovary can be removed before the gonadotoxic therapy and reimplanted after patient's survival, where the ovary is to be cryopreserved during the period of the therapy. However, cryopreservation of the whole ovary is still facing great obstacles, namely the ischemic reperfusion injury and the defective cryopreservation related to the defective ability to universally deliver the cryopreservation/warming solutions through the ovarian vascular bed. Meanwhile, the currently applied technique of ovarian tissue cryopreservation provides limited follicular recovery because many follicles are lost until the development of revascularization post-transplantation. To solve the problems, an innovative system has been developed to insure immediate and universal delivery of the cryopreservation/warming solutions to the graft, in addition to keeping the graft under continuous perfusion before and after cryopreservation, minimizing any chance for microthrombi formation or ischemia-reperfusion. This innovative system can be applied in the following surgical and clinical interventions: 1) Allogeneic ovarian transplantation; 2) Preservation of fertility after systemic chemotherapy or bone marrow transplantation in young females, where the ovaries could be removed before the therapy and exposed to the adequate cryopreservation provided by the system till re-implantation after the patient's survival; 3) The system is also suitable for the corresponding applications on the testicles.

Comparison of different extenders on the recovery and longevity of epididymal sperm from Spix's yellow-toothed cavies (Galea spixii Wagler, 1831)

The aim of this study was to evaluate the performance of cavy (Galea spixii) epididymal sperm following addition to TES or TRIS extenders and using a thermal resistance test (TRT), as well as fluorescence analysis as a complementary method to predict the viability of these gametes. Nine testicle–epididymis complexes were used for sperm collection using a flotation method. Epididymis tails were sliced and one was immersed in 3 ml of TRIS buffer, and the other in 3 ml of TES, for 5 min. After sperm recovery, the samples were subjected to a TRT which involved incubation in a water bath at 37°C for 3 h. During incubation, sample parameters were assessed at 0, 15, 30, 60, 90, 120, 150 or 180 min intervals. Results indicated that the TRIS diluent was more efficient than TES (P < 0.05) for the maintenance of sperm parameters in Spix's yellow-toothed cavies over the whole TRT, maintaining sperm longevity for an extended time. In conclusion, we indicate the use of TRIS diluent for recovery and maintenance of longevity of epididymal sperm from cavies (G. spixii).

Mode of action of cryoprotectants for sperm preservation

Sperm cryopreservation facilitates storage and transport for use in artificial reproduction technologies. Cryopreservation processing, however, exposes cells to stress resulting in cellular damage compromising sperm function. Cryoprotective agents are needed to minimize cryopreservation injury, but at higher concentration they are toxic to cells. In this review, we describe cryoinjury mechanisms, and modes of action of different types of cryoprotective agents. Furthermore, measures are discussed how to minimize toxic effects caused by adding and removing cryoprotective agents. Cryoprotective agents can be divided into permeating and non-permeating agents. Permeating agents such as glycerol can move across cellular membranes and modulate the rate and extent of cellular dehydration during freezing-induced membrane phase transitions. Permeating protectants provide intracellular protection because they are preferentially excluded from the surface of biomolecules thereby stabilizing the native state. Non-permeating agents can be divided into osmotically active smaller molecules and osmotically inactive macromolecules. Both, permeating and non-permeating protectants form a protective glassy state during freezing preserving biomolecular and cellular structures. Freezing extenders for sperm contain salts, buffer compounds, sugars, proteins and lipids, and typically contain glycerol as the main permeating cryoprotective agent providing intracellular protection. Non-permeating protectants including sugars and proteins are used as bulking agents and to increase the glass transition temperature of the freezing extender. Ultra-heat-treated milk and egg yolk are frequently added as membrane modifying agents to enhance the inherent sperm cryostability. The protocol how to use and add cryoprotectants is a compromise between their beneficial and potentially detrimental effects.

Cryotolerance of Sperm from Transgenic Rhesus Macaques (Macaca mulatta)

Cryopreservation is an important tool routinely used in preserving sperm for assisted reproductive technologies and for genetic preservation of unique animal models. Here we investigated the viability of fresh and frozen sperm from rhesus macaques on the basis of motility, membrane integrity, and acrosome integrity. Sperm motility was determined by visual evaluation; membrane and acrosome integrity were assessed simultaneously through triple staining with Hoechst 33342, propidium iodide, and fluorescein isothiocyanate-peanut agglutinin. We compared thawed semen that had been cryopreserved by using 2 different media with fresh semen from wildtype (WT) macaques; fresh semen from a model of Huntington disease (HD) with fresh WT semen; and fresh HD with cryopreserved-thawed HD semen. Our new freezing media (TEST EQ) preserved the acrosome better, with less net damage, than did traditional TEST (egg yolk extender containing TES and Tris) media. In addition, the percentage of membrane-damaged cells was similar in fresh HD semen (38.6%±2.9%) and WT semen (35.5%±1.9%). Membrane and acrosomal damage were not different between HD and WT sperm after cryopreservation and subsequent thawing. Furthermore, cryopreservation had similar negative effects on the motility of HD and WT sperm. These data illustrate that semen from a rhesus macaque model of HD is similarly cryotoleratant to that from WT animals.

Slow cryopreservation is not superior to vitrification in human spermatozoa; an experimental controlled study

BACKGROUND

Spermatozoa cryopreservation is used for the management of infertility and some other medical conditions. The routinely applied cryopreservation technique depends on permeating cryoprotectants, whose toxic effects have raised the attention towards permeating cryoprotectants-free vitrification technique.

OBJECTIVE

To compare between the application of slow cryopreservation and vitrification on human spermatozoa.

MATERIALS AND METHODS

This was an experimental controlled study involving 33 human semen samples, where each sample was divided into three equal parts; fresh control, conventional slow freezing, and permeating cryoprotectants-free vitrification. Viability and mitochondrial membrane potential (MMP) of control and post-thawing spermatozoa were assessed with the sperm viability kit and the JC-1 kit, respectively, using fluorescence-activated cell sorting analysis.

RESULTS

Significant reduction of the progressive motility, viability and MMP was observed by the procedure of freezing and thawing, while there was not any significant difference between both cryopreservation techniques. Cryopreservation resulted in 48% reduction of the percentage of viable spermatozoa and 54.5% rise in the percentage of dead spermatozoa. In addition, high MMP was reduced by 24% and low MMP was increased by 34.75% in response to freezing and thawing. Progressive motility of spermatozoa was correlated significantly positive with high MMP and significantly negative with low MMP in control as well as post-thawing specimens (r=0.8881/ -0.8412, 0.7461/ -0.7510 and 0.7603/ -0.7839 for control, slow and vitrification respectively, p=0.0001).

CONCLUSION

Although both cryopreservation techniques have similar results, vitrification is faster, easier and associated with less toxicity and costs. Thus, vitrification is recommended for the clinical application.

Biobanking: The Future of Cell Preservation Strategies

With established techniques cryopreservation is often viewed as an "old school" discipline yet modern cryopreservation is undergoing another scientific and technology development growth phase. In this regard, today's cryopreservation processes and cryopreserved products are found at the forefront of research in the areas of discovery science, stem cell research, diagnostic development and personalized medicine. As the utilization of cryopreserved cells continues to increase, the demands placed on the biobanking industry are increasing and evolving at an accelerated rate. No longer are samples providing for high immediate post-thaw viability adequate. Researchers are now requiring samples where not only is there high cell recovery but that the product recovered is physiologically and biochemically identical to its pre-freeze state at the genominic, proteomic, structural, functional and reproductive levels. Given this, biobanks are now facing the challenge of adapting strategies and protocols to address these needs moving forward. Recent studies have shown that the control and direction of the molecular response of cells to cryopreservation significantly impacts final outcome. This chapter provides an overview of the molecular stress responses of cells to cryopreservation, the impact of the apoptotic and necrotic cell death continuum and how studies focused on the targeted modulation of common and/or cell specific responses to freezing temperatures provide a path to improving sample quality and utility. This line of investigation has provided a new direction and molecular-based foundation guiding new research, technology development and procedures. As the use of and the knowledge base surrounding cryopreservation continues to expand, this path will continue to provide for improvements in overall efficacy and outcome.