Partial deoxygenation of extender improves sperm quality, reduces lipid peroxidation and reactive oxygen species during cryopreservation of buffalo (Bubalus bubalis) semen

Effects of propolis-loaded nanoliposomes fortification in extender on buffalo semen cryopreservation

Buffalo sperm is sensitive to cryoinjuries, thus improving sperm cryoresistance is a critical approach for wide spreading the assisted reproductive technologies in buffalo. The intention of this work was to assess the effect of propolis-loaded in nanoliposomes (PRNL) supplementation of semen extender on semen quality, antioxidant status and some apoptotic genes of cryopreserved buffalo semen. PRNL were prepared using cholesterol (Chol) as well as soybean lecithin and their physicochemical properties were characterized. Egyptian buffalo bulls (4-6 years) were involved, and the semen samples were collected using the artificial vagina method. Buffalo semen was pooled (n = 25 ejaculates) and cryopreserved in tris extender containing PRNL at 0 (PRNL0), 2 (PRNL2), 4 (PRNL4) and 6 µg/mL (PRNL6), respectively. The PRNL had a size of 113.13 nm and a negative zeta potential (- 56.83 mV). Sperm progressive motility, viability, membrane integrity, abnormalities, chromatin damage, redox status, apoptosis status, and apoptotic genes were investigated after post-thawed buffalo semen. Using 2 or 4 µg/mL PRNL significantly increased sperm progressive motility, viability, and membrane integrity, while sperm abnormalities and the percentage of chromatin damages were the lowest in PRNL2 group. Moreover, the PRNL2 group exhibited the best results for all antioxidative activities (TAC, SOD, GPx and CAT) with significantly higher levels than the other groups (P < 0.05). The levels of ROS and MDA were significantly lower in the PRLN2 compared with other groups. The sperm caspase 3 enzyme activities showed the lowest values in PRNL2 groups followed by PRNL4 and PRNL6 groups with significant differences compared with the control. Adding 2 µg/mL PRNL to freezing media significantly reduced apoptotic genes such as Bax and Caspase 3 in sperm, while significantly increase in Bcl2 expression compared with the control (P < 0.001). The expression of Bcl2, Caspase 3 and Bax genes in sperm were not affected by the 6 µg/mL PRNL addition (P > 0.05). The electron micrography descriptions exemplified that the fortification of 2 or 4 µg/mL PRNL maintained the acrosomal and plasma membrane integrities as well as sustained the ultrastructure integrity of the cryopreserved buffalo spermatozoa when compared with control group, whereas the 6 µg/mL of PRNL demonstrated highest injury to the acrosome and plasma membranes. Results show supplementation of the buffalo freezing extender with 2 or 4 µg/mL of PRNL enhanced post-thawed sperm quality via boosting the antioxidant indices, diminishing the oxidative stress and apoptosis as well as maintained the ultrastructure integrity of frozen-thawed buffalo sperm.

Sulforaphane inclusion in a freezing medium augments post-thaw motility, functional and biochemical features, and fertility potential of buffalo (Bubalus bubalis) spermatozoa

Sulforaphane is a natural and highly effective antioxidant safeguarding the reproductive system, and alleviate oxidative stress. This study was designed in order to elaborate L-sulforaphane effect on semen quality, biochemical parameters, and fertility of buffalo (Bubalus bubalis) spermatozoa. Semen was collected from five buffalo bull with artificial vagina (42 °C) three times and evaluated for volume, consistency (color), motility, and sperm concentration. After critical examination, semen was diluted (50 × 10⁶ spermatozoa per ml, 37 °C) in extenders with (2 μM, 5 μM, 10 μM, and, 20 μM) or without (control) sulforaphane, cooled (from 37 to 4 °C), equilibrated (4 °C), filled (straws, 4 °C), and cryopreserved (LN₂, -196 °C). Data analysis exhibited that sulforaphane addition in extender augments total motility (%, 10 μM, and 20 μM than control), progressive motility (%), and rapid velocity (%, 20 μM than control), and velocity parameters (average path velocity, μm/s, straight line velocity, μm/s and curved linear velocity, μm/s, 20 μM than control, and 2 μM). Moreover, sulforaphane augments functional features (membrane functionality, mitochondrial potential, and acrosome integrity) of buffalo sperm (20 μM than control). Sulforaphane preserves biochemical features of seminal plasma of buffalo i.e., Calcium (μM), and total antioxidant capacity (μM/L), followed by reduction in lactate dehydrogenase (IU/L), reactive oxygen species (10⁴ RLU/20 min/ 25 million), and lipid peroxidation (μM/ml) in 20 μM than control. Lastly, sulforaphane augments fertility rate of buffalo sperm at 20 μM than control, and 2 μM. Conclusively the existing study revealed that adding L-sulforaphane (20 μM) in a freezing medium augments motilities, kinematics, functional parameters, and fertility rate of buffalo spermatozoa. Correspondingly, sperm favorable biochemical features were also augmented with sulforaphane followed by reduction in oxidative stress parameters. Further studies are highly recommended to define the particular mechanism of action of sulforaphane in augmenting buffalo post-thawed semen quality, and in vitro fertility potential.

An evidence of Humanin-like peptide and Humanin mediated cryosurvival of spermatozoa in buffalo bulls

Buffalo spermatozoa are vulnerable to cryo-injuries due to inherent deficiency of endogenous antioxidants, high polyunsaturated fatty acids (PUFA) content in plasma membrane and low cholesterol/phospholipid (C/P) ratio. Humanin is a potent cytoprotective agent that protects the cells against oxidative stress and apoptosis. The present study was designed to establish the presence of Humanin in buffalo and effect of Humanin supplementation on freezability of buffalo spermatozoa. Indirect immunofluorescence test revealed presence of Humanin in ejaculated and epididymal spermatozoa, and, elongated spermatids and interstitial space in the testicular tissue section. Humanin levels in seminal plasma were significantly and positively correlated with sperm concentration and individual progressive motility (IPM) in good (n = 22; IPM >70%) and poor (n = 10; IPM <50%) quality ejaculates. For supplementation studies, a total of 24 ejaculates (IPM ≥70%) were collected and each ejaculate was then divided into four aliquots. First aliquot was diluted with egg yolk-tris-glycerol (EYTG) extender without Humanin and served as control group (Group I). Rest three aliquots were diluted with extender containing 2 (Group II), 5 (Group III) and 10 μM Humanin (Group IV), respectively. Semen was cryopreserved using standard protocol and evaluated at pre-freeze for lipid peroxidation (LPO) and post-thaw stages for spermatozoa kinematics, LPO, mitochondrial membrane potential (MMP), capacitation, apoptotic status and DNA integrity. The treatment group that showed best results (5 μM) was compared with control group for in vitro fertility assessment by homologous zona binding assay. The LPO levels were lower (p < 0.05) in 5 and 10 μM Humanin supplemented group. The MMP and DNA integrity were higher (p < 0.05) in 5 μM group than other groups. F-pattern was higher (p < 0.05) and B-pattern was lower (p < 0.05) in 5 and 10 μM Humanin supplemented groups. Lower apoptotic and higher viable spermatozoa (p < 0.05) were observed in 5 μM Humanin group. The mean number of spermatozoa bound to zona pellucida was higher (p < 0.05) in 5 μM Humanin treated group than the control group. The study established the presence of Humanin in buffalo spermatozoa and seminal plasma for very first time and concluded that Humanin supplementation at 5 μM concentration improves the freezability and in vitro fertility of buffalo spermatozoa.

Efficacy of soursop juice extender on rooster semen quality, oxidative activity and spermatozoa kinematics

African medicinal plant like soursop (Annona muricate L.) within annonaceae are known for their biological, therapeutic, and pharmacological properties with little or no toxicity. The use of such plant requires good knowledge of the toxicity dosage, purity, suitable extraction solvent and adverse effects. The leaves, seeds, fruits, barks, and roots of African medicinal plants have been used for various nutraceuticals and functional effects according to African folk medicine. The aim of this study is to evaluate the semen quality, oxidative activity and spermatozoa kinematics of rooster semen in soursop juice extender. About 30 roosters were used for the in vitro analysis. Semen was collected twice a week for 2 weeks through dorsal-abdominal massage technique. The evaluation was done hourly until semen quality declined at the 5th-hour. The pooled semen was allotted to seven treatments of semen extenders as undiluted semen, dextrose saline, 10% soursop juice extender, 20% soursop juice extender, 30% soursop juice extender, 40% soursop juice extender, and 50% soursop juice extender for the study. The percentage motility, progressive motility, nonprogressive motility, curvilinear velocity, average path velocity, straight line velocity, linearity, straightness, amplitude of lateral head, beat cross frequency and wobble were analyzed using computer aided sperm analysis. Oxidative status (antioxidant activity and lipid peroxidation) was determined by assay. Result of rooster semen at room temperature and after 1-hour dilution showed that percentage motility, nonprogressive motility, and average path velocity were significantly (P < 0.05) reduced by different soursop juice extenders compared to undiluted semen. After 2-hour dilution of rooster semen, nonprogressive motility, average path velocity, curvilinear velocity, straight line velocity, wobble, liveability and amplitude of lateral head parameters were significantly (P < 0.05) increased by different soursop juice extenders compared to undiluted semen. Antioxidant activity and lipid peroxidation in both room temperature and after 5-hour dilution were affected by different soursop juice extenders in rooster semen. In conclusion, supplementation of soursop juices as an extender to rooster undiluted semen played an improvement role on spermatozoa fertility and oxidative status during processing or preserving ejaculates for insemination.

The Protective Role of Melatonin in Sperm Cryopreservation of Farm Animals and Human: Lessons for Male Fish Cryopreservation

Simple Summary

In recent years, cryopreservation of fish sperm has been a rapidly evolving technique that contributes both to the improvement of genetic reproduction programs and the proper management of broodstock as well as to ensuring the viability of endangered species. However, this technique can cause significant damage to sperm, making the use of cryoprotectants and antioxidants in cryopreservation solutions imperative. The hormone melatonin has demonstrated positive effects on the cryopreservation of sperm in both farm animals and humans. Therefore, the plethora of research that has been conducted on animals and humans could be expanded to fish cryopreservation, making melatonin potentially a very promising alternative cryoprotectant.

Abstract

Cryopreservation is a technique that offers various advantages, especially in fish, among others, that makes the reproduction of species easier through a constant supply of sperm, synchronization of the gamete availability of both sexes, storage of semen for genetic improvement programs, reduction in the cost by eliminating the need to maintain male broodstock, and conserving the gametes of endangered species. However, freezing and warming procedures for cryopreservation lead to a reduction in the quality and viability of cryopreserved sperm because of oxidative stress. For this reason, the enrichment of extender media with antioxidants is a common method of cryopreservation of the semen of several fish species. Recently, many studies have been published for the protective role of antioxidants and especially of melatonin on male fertility preservation both in farm animals and humans, demonstrating the beneficial effects of melatonin as a sperm cryoprotectant. On the other hand, very few studies were conducted using melatonin as an antioxidant in different male fish species for semen cryopreservation. We conclude that the use of moderate concentrations of melatonin are beneficial to semen preservation, and the mechanisms through which melatonin acts positively on spermatozoa need to be further investigated to establish improvement protocols for cryopreservation in fish species.

Cryoprotectant With A Mitochondrial Derived Peptide, Humanin, Improves Post-Thaw Quality Of Buffalo Spermatozoa

BACKGROUND: Semen cryopreservation results in deleterious effects on spermatozoa, including lipid peroxidation and a reduction in the total antioxidant components of seminal plasma. The ultimate outcome of these changes is a reduction in post-thaw semen quality. A mitochondrial derived peptide, humanin, a potent cytoprotective and antioxidant agent was used in the present study. OBJECTIVE: To evaluate the efficacy of a mitochondrial-derived peptide, humanin to improve the post-thaw quality of buffalo spermatozoa. MATERIALS AND METHODS: A total of 18 ejaculates from three Murrah buffalo bulls (n=6 each) were collected. Each ejaculate was divided into four aliquots. The first aliquot was diluted with standard EYTG dilutor (Group I, control), whereas the other three aliquots were diluted with EYTG supplemented with 2 μM (Group II), 5 μM (Group III) and 10 μM humanin (Group IV), respectively. Semen was evaluated for physico-morphological and functional attributes such as progressive motility, viability, abnormality, acrosome integrity, plasmamembrane integrity of fresh samples, pre-freeze and post-thaw stages. Oxidative stress parameters [lipid peroxidation (LPO) and total antioxidant capacity (TAC)] were also measured at the pre-freeze and post-thaw stages. RESULTS: Humanin s upplementation resulted in significantly higher (p≤0.05) post- thaw motility in all treatment groups and, higher (p≤0.05) viability in Groups III and IV in comparison to the control at the post-thaw stage. Spermatozoa with intact acrosome and plasma membran e were higher (p≤0.05) in Groups III and IV as compared to Group s I and II. The LPO levels at the post- thaw stage were found to be lower (p≤0.05) in all treatment groups versus the control group, whereas, higher (p≤0.05) TAC value s were recorded in Groups III and IV in comparison to the control and Group II. CONCLUSION: Humanin supplementation in the extender improved the freezabilty of buffalo spermatozoa.

Optimization of dissolved oxygen levels in extender prevents development of cryocapacitation like changes, oxidative stress and augments zona binding capacity of crossbred bull spermatozoa

The present study was undertaken to determine the efficacy of partial deoxygenation of extender at constant temperature (35°C) in freezability of crossbred bull semen. The dissolved oxygen (DO) levels were reduced by the use of newly developed technique of nitrogen effervescence at a flow rate of 2-3 bubbles per second. Four different levels of oxygen in semen extender, that is 11.7, 2, 4 and 8 ppm as control (Group-I), Group-II, Group-III and Group-IV, respectively, were used to assess the effect of partial deoxygenation on semen quality parameters. The 4 ppm level of DO resulted in higher (p < 0.05) progressive motility in comparison with non-treated group at post-thaw stage, whereas reduction up to 2 ppm resulted in drastic fall in motility. Oxidative stress status revealed low superoxide dismutase (SOD) and total antioxidant capacity (TAC) in Group-II, whereas higher (p < 0.05) SOD and TAC activities were observed in Group-III in comparison with non-treated group at pre-freeze and post-thaw stages. The sperm-zona binding at 4 ppm level of DO was significantly higher than control group, 2 and 8 ppm levels of DO. In conclusion, reduction of DO in the extender up to 4 ppm reduced oxidative stress and improved in vitro fertility of crossbred bull spermatozoa.

Impact of Oxidative Stress on Male Reproduction in Domestic and Wild Animals

Oxidative stress occurs when the levels of reactive oxygen species (ROS) overcome the antioxidant defenses of the organism, jeopardizing several biological functions, including reproduction. In the male reproductive system, oxidative stress not only impairs sperm fertility but also compromises offspring health and survival, inducing oxidative damage to lipids, proteins and nucleic acids. Although a clear link between oxidative stress and male fertility disorders has been demonstrated in humans and laboratory rodents, little information is available about the implications of impaired redox homeostasis in the male fertility of domestic and wild animals. Therefore, this review aims to provide an update regarding the intrinsic and extrinsic factors that are associated with oxidative stress in the male reproductive system and their impact on the reproductive performance of domestic and wild animals. The most recent strategies for palliating the detrimental effects of oxidative stress on male fertility are reviewed together with their potential economic and ecological implications in the livestock industry and biodiversity conservation.

Improving the quality and in vitro fertilization rate of frozen-thawed semen of buffalo (Bubalus bubalis) bulls with the inclusion of vitamin B12 in the cryopreservation medium

This study was designed to evaluate the effects of vitamin B₁₂ in cryopreservation medium on frozen-thawed semen of buffalo (Bubalus Bubalis) bulls. Semen from five bulls (fertility-proven) were diluted in five aliquots not supplemented (control), or supplemented with 1, 2, 4, or 5 mg/mL of vitamin B₁₂ and evaluated using the Computer Assisted Sperm motion Analysis, antioxidant enzymes, lipid peroxidation (LPO), reactive oxygen species (ROS), ATP concentrations, and in vitro fertilization rate (%). Sperm progressive motility, rapid velocity (%), mitochondrial potential, and acrosome integrity were greater (P < 0.05) with supplementation of 4, and 5 mg/mL vitamin B₁₂ than the control sample. Similarly, compared with the control, samples with 5 mg/mL vitamin B₁₂ supplementation had markedly greater average-path, straight-line, and curved-line velocities (μm/sec). Semen samples supplemented with 2, 4 and 5 mg/mL vitamin B₁₂ had greater concentrations of GPx (U/mL) and SOD (U/mL), whereas LPO (μM/mL) was less (P < 0.05) compared with the control sample. Seminal plasma ROS concentrations (10⁴/25 × 10⁶) were less in the 5 mg/mL vitamin B₁₂ supplemented than control sample. Semen samples supplemented with 5 mg/mL of vitamin B₁₂ had greater concentrations of ATP than control and the 1 mg/mL vitamin B₁₂ supplemented sample. Semen samples supplemented with 5 mg/mL of vitamin B₁₂ had greater plasmalemma and DNA integrities (%) than the control sample. In summary, vitamin B₁₂ supplementation augments semen quality, as evidenced by values for CASA variables, antioxidant enzymes, and ATP concentrations, which may occur as a consequence of inhibition in LPO and ROS production by buffalo spermatozoa.

Exploring the role of E.coli derived enzyme, Oxyrase, as an oxygen scavenger to improve the cryotolerance of spermatozoa of Sahiwal bull

The current study intended to optimize the concentration of Oxyrase in the semen dilutor and to evaluate its effect on freezability of spermatozoa of Sahiwal bulls. Supplementation of Oxyrase at 0.125 IU/mL concentration significantly reduced dissolved oxygen (DO) in the dilutor to 4 ppm in 16-18 min at 35 °C. For supplementation studies, a total of 24 ejaculates were categorized into poor and good ejaculates categories (n = 12 each) based on their initial progressive motility. Each ejaculate was further divided into two aliquotes. The first aliquote was diluted with tris-egg yolk extender without Oxyrase (control group) whereas, in the treatment group, Oxyrase was supplemented at the concentration of 0.125 IU/mL of extender. The parameters evaluated include cholesterol and plasma membrane phospholipids (PMP) at fresh, while IPM, acrosomal and plasma membrane integrity, cholesterol, PMP and oxidative stress parameters like lipid peroxidation (LPO), total antioxidant capacity (TAC) and reactive oxygen species (ROS) were evaluated at pre-freeze and post-thaw stages. The IPM and acrosomal intactness were higher (p < 0.05) in treatment group at post-thaw stage in good ejaculates. Oxyrase supplementation resulted in lower (p < 0.05) cholesterol leakage in both categories and lower (p < 0.05) LPO in good ejaculates at post-thaw stage. No statistical difference in ROS was observed between control and treatment groups at all stages whereas, level of TAC was higher (p < 0.05) in the treatment group compared to control group at post-thaw stage of both categories. Therefore, Oxyrase as an oxygen scavenging agent could preserve the post-thaw quality of Sahiwal bull spermatozoa.

Escherichia coli membrane-derived oxygen-reducing enzyme system (Oxyrase) protects bubaline spermatozoa during cryopreservation

The objective of this study was to determine the effectiveness of deoxygenation of semen extender using Escherichia coli membrane-derived oxygen scavenger (Oxyrase) on post-thaw quality of buffalo (Bubalus bubalis) spermatozoa. Sixteen semen ejaculates, four each from four bulls, were each divided into five equal fractions, diluted using Tris-egg yolk extender supplemented with different concentrations of Oxyrase (0, 0.3, 0.6, 0.9, and 1.2 U/ml), designated as treatments T1, T2, T3, T4, and T5, respectively, and cryopreserved. Immediately after thawing, Oxyrase did not improve sperm kinetics and motility; however, it improved the keeping quality (significantly lower deterioration of post-thaw sperm motility after incubation for 120 min) in T3. Further, T3 reduced (p < .05) cholesterol efflux and protected the intactness of the sperm plasma membrane. Flow cytometry with Fluo-3 AM/propidium iodide (PI) dual staining revealed the highest (p < .05) proportion of live spermatozoa with low intracellular calcium in T3. Oxyrase supplementation protected spermatozoa from premature capacitation which was confirmed by low expression of tyrosine-phosphorylated proteins (32, 75, and 80 kDa) and a relatively lower percentage of F-pattern (uncapacitated spermatozoa) in chlortetracycline assay. Importantly, the Oxyrase fortification decreased superoxide anion in a dose-dependent manner indicating reduced availability of oxygen at sperm mitochondrial level. Similarly, in Oxyrase-fortified sperm, malondialdehyde concentration, an index of lipid peroxidation, is also reduced in a dose-dependent manner. In conclusion, we demonstrate that deoxygenation of buffalo semen by Oxyrase has the potential of improving post-thaw sperm quality by overcoming the problem of cryocapacitation and oxidative damage during cryopreservation process.

Supplementing extender with anandamide enhances quality of low sperm doses during cryopreservation in bulls

The present study explored the effect of anandamide supplementation in the extender on quality of low sperm doses during cryopreservation in Sahiwal bulls. Each fresh semen sample was split into eight aliquots (I, II, III, IV, V, VI, VII and VIII). The aliquots I, II, III and IV were taken as control and diluted to 20, 15, 10 and 5 million spermatozoa/0.25 ml respectively. The aliquots V, VI, VII and VIII were diluted with extender (supplemented with anandamide at 1 µM/ml of extender) to 20, 15, 10 and 5 million spermatozoa/0.25 ml respectively. This was followed by filling of diluted semen into French mini straws, equilibrated at 4°C of 4 hr and cryopreserved. The results revealed that the proportions of motile spermatozoa, live spermatozoa and live acrosome intact spermatozoa were significantly (p < .05) higher in all anandamide-treated sperm doses compared to control. The proportions of moribund spermatozoa, dead acrosome intact spermatozoa and capacitated spermatozoa were significantly (p < .05) reduced in all anandamide-treated sperm doses compared to control, with no difference in proportion of dead acrosome-reacted spermatozoa. In conclusion, anandamide supplementation in the extender increases the post-thaw quality of low sperm doses during cryopreservation in bulls.

Nano-purification of raw semen minimises oxidative stress with improvement in post-thaw quality of buffalo spermatozoa

The study consisted of application of anti-ubiquitin antibodies (Abs)-coated iron oxide-nanoparticles (IONPs) for minimisation of oxidative stress to contemporary live spermatozoa from the raw semen. Round-shaped IONPs (12.09 ± 0.91 nm) after two-stage functionalisation (silanisation and pegylation) were conjugated with Abs. Four aliquots from each of the 24 ejaculates (4 buffalo bulls) formed Control (Group I) and treatment (II, III and IV) groups; each containing 150 ± 25 million dead/damaged spermatozoa. IONPs-Abs complex were added at ratio of 1:1 (0.5 µg/ml), 1:2 (1.0 µg/ml) and 1:4 (2.0 µg/ml), respectively, in Groups II, III and IV. The semen quality parameters showed improvement at lag-stage (post-nano-purification before processing for cryopreservation). The mean post-thaw motility (%) in Group IV was found to be greater (p < .05) than Group I. Moreover, the overall DNA integrity (%) at post-thaw stage was improved in the nano-purified semen samples. The value of malondialdehyde was greater (p < .001) in Group I than Groups II, III and IV. The mean total antioxidant capacity and superoxide dismutase (U/mg protein) activity values in Group IV was greater (p < .05) than Group I. The study results show that IONPs conjugated with anti-ubiquitin Abs at 2.0 µg/ml can be an effective dose for depletion of dead/damaged spermatozoa from buffalo ejaculates to minimise oxidative stress.

Modification of French mini-straw plug position for cryopreservation of small doses of bull sperm

Greater than optimal diluting of semen for producing a large number of doses containing relatively small numbers of sperm can lead to compromised quality of sperm, post-thawing. In the present study the French mini-straw plug position was modified and the effect of re-positioning was evaluated on the quality of sperm after thawing subsequent to cryopreservation of small doses of sperm. Four types of mini-straws were used based on the position of cotton plug including no plug displacement (Type 1; Manufacturers location for plug-placement in 0.25 mL French mini-straws), and Type II, III, and IV with re-positioning the cotton plug being 2.5, 5, and 7.5 cm, respectively, further from the manufacturer's placement location. Each ejaculate was proportioned into four Aliquots (I, II, III, and IV) and diluted to 80, 60, 40, and 20, million sperm/mL, respectively. Aliquot I was placed in all types of straws, while Aliquots II, III, IV were placed only in Type I straws. Semen straws were equilibrated, cryopreserved and sperm kinetic and functional variables were evaluated post-thawing. The results indicate that in Aliquots III and IV there were lesser (P < 0.05) values for sperm kinetic and function variables compared with sperm from Aliquot I (i.e., unmodified mini-straw). In conclusion, cryopreservation of small doses of sperm in modified French mini-straws resulted in acceptable values for kinetic and function variables, post-thawing.

Cold case: Small animal gametes cryobanking

Germplasm preservation of animals, whether they are valuable domestic breeds or rare species, is the main goal of gamete cryobanking. Dogs and cats act as models for this purpose thanks to the wide availability of biological material which can be employed to experiment protocols that can then be applied to wild animals. This review is focused on spermatozoa, oocytes and gonadal tissues cryobanking in small domestic animals, which is still an unsolved case. Like in a courtroom, evidences of cryoinjuries affecting cellular structures will be presented, penalties as loss of functionality due to cellular alterations will be described, and appeal as strategies to protect gametes from damages or rescue their functionality will be discussed. Differences and similarities between single cell or tissue cryopreservation will be highlighted, together with the rationale for the choice of one type of preservation or another and the fundamental principles which they are based on. The deep analysis of different aspects that still hamper the success of cryopreservation in small animals can help clarify where research is most needed. Therefore, as in a cold case, investigation should remain open in order to hopefully find the solution and make these procedures more and more efficient in the future.

Trehalose protects testicular tissue of dairy goat upon cryopreservation

The aim of this study was to investigate whether the addition of trehalose to cryomedia reduces cellular damage and improves gene expression in cryopreserved dairy goat testicular tissues. Testicular tissues were cryopreserved in cryomedia without or with trehalose at a concentration of 5%, 10%, 15%, 20% or 25%. Cryopreserved testicular tissues were analysed for TUNEL-positive cell number, expression of BAX, BCL-2, CREM, BOULE and HSP70-2. Isolated Leydig cells from cryopreserved tissue were cultured, and spent medium was evaluated for testosterone level. The results showed that though the TUNEL-positive cell number increased in cryopreserved testicular tissues, the presence of trehalose reduced apoptotic cell number significantly. Quantitative real-time polymerase chain reaction results showed that although the expression of BAX was upregulated following cryopreservation, the presence of trehalose downregulates it in cryopreserved testicular tissues. Expression of BCL-2, CREM, BOULE and HSP70-2 was downregulated following cryopreservation but the presence of trehalose significantly upregulated their expression in cryopreserved testicular tissues. Leydig cells isolated from testicular tissues cryopreserved with trehalose produced higher testosterone than the one without it (control). These results suggest that trehalose has a protective role in cryopreservation of dairy goat testicular tissue, and the most suitable trehalose concentration for cryopreservation is 15%.

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.

Possible mechanisms of cholesterol-loaded cyclodextrin action on sperm during cryopreservation

Artificial insemination (AI) with cryopreserved semen has a pivotal role in wider dissemination of germplasm of elite livestock and also for conservation of various endangered species. Cryopreservation allows storage of semen for a prolonged period of time and facilitates greater exchange of genetic material among distant populations. Cryopreservation, however, leads to certain deleterious effects on sperm including premature induction of the acrosome reaction, reduced sperm motility and viability, and impaired sperm DNA integrity and fertility. During cooling procedures, membrane phase transitions take place, which result in micro-domain formation from aggregation of lipids, leading to impaired functions of the sperm membrane, and gap formation between gel and fluid domains. Cyclodextrins are produced by enzymatic degradation of starch and possess a unique feature, that when added alone to sperm cyclodextrins facilitate the removal of cholesterol from the membrane. When preloaded with cholesterol, however, cyclodextrins stimulate the insertion of cholesterol into the sperm membrane due to presence of a hydrophobic core in addition to an outer hydrophilic face. Treating sperm of various species with cholesterol-loaded cyclodextrin improves the quality of sperm during cryopreservation. It is still not clearly known how cholesterol-loaded cyclodextrin functions at sperm cells to enhance the survival during cryopreservation. The present review, therefore, highlights possible mechanisms of cholesterol-loaded cyclodextrin action on sperm during cryopreservation.