Electromagnetic field in human sperm cryopreservation improves fertilizing potential of thawed sperm through physicochemical modification of water molecules in freezing medium

Effects of glucose and trehalose on tris-citric acid-egg yolk-fructose diluents for semen cryopreservation in goat

Objectives

This study aimed to examine the impacts of the wide range of concentrations of glucose and trehalose on the tris-citric acid-egg yolk-fructose (TCEF) extenders for cryopreservation of goat semen.

Materials and Methods

The sperm sample was pooled, washed, and diluted in control (TCEF without glucose and trehalose), TCEF + glucose (75, 150, 450, and 900 mm), and TCEF + trehalose (75, 150, 450, and 900 mm). After equilibrations, the semen straws were frozen under LN2 in the LN2 tank. After LN2 storage, the straws were thawed at 37°C for 30 seconds. The sperm parameters of all study groups were checked after equilibration and freezing.

Results

After equilibration, the progressive motility (PM), total motility (TM), and viability of sperm in G-75, G-150, G-450, T-75, T-150, and T-450 were not significantly different (p < 0.05) from those in control. After cryopreservation and thawing, the PM, TM, and plasma membrane integrity (PMI) of T-150 were significantly higher (p < 0.05) than in control, G-75, G-900, T-75, and T-900. The viability of sperm in T-150 was substantially higher (p < 0.05) than in the control, whereas there was no significant difference among the control, G-75, G-900, T-75, and T-900. However, the acrosome integrity (AI) of sperm in G-900 was significantly decreased (p < 0.05) compared to the control, G-75, G-150, G-450, T-75, T-150, and T-450.

Conclusion

According to the findings, the supplementation of 150 mm trehalose in the TCEF diluent was more efficient for sperm cryopreservation in the buck as reflected by PM, TM, viability, PMI, and AI.

Effect of Magnetized Freezing Extender on Membrane Damages, Motility, and Fertility of Boar Sperm Following Cryopreservation

Magnetized water is defined as the amount of water that has passed through a magnet. The magnetic field weakens the hydrogen bonds between the water molecules, leading to the magnetized liquid acquiring special characteristics such as easy supercooling and forming smaller ice crystals. We researched the influences of a magnetized freezing extender on cell membrane damage and in vitro fertilization of boar sperm during cryopreservation. The freezing extenders were passed through 0, 2000, 4000, and 6000 gausses (G) of magnetic devices using a liquid cycling pump system and then used for the sperm freezing process. The damage to plasma, acrosomal, and mitochondrial membranes in frozen-thawed spermatozoa was investigated by flow cytometry, and motility was assessed using the CASA system. The fertility of frozen-thawed sperm was estimated using in vitro fertilization. The damage to the membranes was significantly decreased in the magnetized freezing extender by the 6000 G magnetic field compared to that of the control in frozen-thawed sperm, and motility was increased in the 6000 G group. Although there were no significant differences in the cleavage rates of in vitro fertilized oocytes among the treatment groups, the ratio of blastocyst formation increased in the magnetized freezing extender groups compared with that in the control group. The number of blastocysts was significantly higher in the 4000 G group than in the 0 G group. In conclusion, these results suggest that a magnetized freezing extender could improve the freezability of sperm and the development of oocytes fertilized in vitro with frozen-thawed sperm.

Sperm cryopreservation: current status and future developments

The cryopreservation of spermatozoa is an important reproductive technology for the preservation of fertility in man and animals. Since the serendipitous discovery of glycerol as an effective cryoprotectant in 1947, sperm cryopreservation has undergone many changes in terms of the freezing methods employed, the rates at which samples are frozen and thawed, and the media used to preserve sperm functionality and DNA integrity. An extensive literature survey has been conducted addressing the cryoprotectants employed for both animal and human semen and the freezing protocols utilised. The results indicate that glycerol remains the dominant cryoprotective agent, usually incorporated into a balanced salt solution containing energy substrates, buffers, osmolytes and protein in the form of human serum albumin (human) or skimmed milk (animal). Realisation that some of the damage observed in cryostored cells involves the generation of reactive oxygen species during the thawing process, has prompted many studies to assess the relative merits of incorporating antioxidants into the cryopreservation media. However, in the absence of systematic comparisons, there is currently no consensus as to which antioxidant combination might be the most effective. Utilising our fundamental understanding of cryodamage to optimise cryopreservation protocols for each species will be important in the future.

Beneficial effects of trehalose and gentiobiose on human sperm cryopreservation

The protection of human sperm during cryopreservation is of great importance to infertility. Recent studies have shown that this area is still a long way from its ultimate aim of maintaining the maximum viability of sperm in cryopreservation. The present study used trehalose and gentiobiose to prepare the human sperm freezing medium during the freezing-thawing. The freezing medium of sperm was prepared with these sugars, and the sperm were then cryopreserved. The viable cells, sperm motility parameters, sperm morphology, membrane integrity, apoptosis, acrosome integrity, DNA fragmentation, mitochondrial membrane potential, reactive oxygen radicals, and malondialdehyde concentration was evaluated using standard protocols. A higher percentage of the total and progressive motility, rate of viable sperm, cell membrane integrity, DNA and acrosome integrity, and mitochondrial membrane potential were observed in the two frozen treatment groups compared to the frozen control. The cells had less abnormal morphology due to treatment with the new freezing medium than the frozen control. The higher malondialdehyde and DNA fragmentation were significantly observed in the two frozen treatment groups than in the frozen control. According to the results of this study, the use of trehalose and gentiobiose in the sperm freezing medium is a suitable strategy for sperm freezing to improve its motion and cellular parameters.

Cryopreservation of Semen in Domestic Animals: A Review of Current Challenges, Applications, and Prospective Strategies

Cryopreservation is a way to preserve germplasm with applications in agriculture, biotechnology, and conservation of endangered animals. Cryopreservation has been available for over a century, yet, using current methods, only around 50% of spermatozoa retain their viability after cryopreservation. This loss is associated with damage to different sperm components including the plasma membrane, nucleus, mitochondria, proteins, mRNAs, and microRNAs. To mitigate this damage, conventional strategies use chemical additives that include classical cryoprotectants such as glycerol, as well as antioxidants, fatty acids, sugars, amino acids, and membrane stabilizers. However, clearly current protocols do not prevent all damage. This may be due to the imperfect function of antioxidants and the probable conversion of media components to more toxic forms during cryopreservation.

Static magnetic field halves cryoinjuries of vitrified mouse COCs, improves their functions and modulates pluripotency of derived blastocysts

This study was performed with the aim of evaluating the influence of static magnetic field (SMF) of 60 mT on mouse Cumulus Oocytes Complexes (COCs) vitrification. The COCs were vitrified in the presence (Vit_SMF⁺) and absence of SMF (Vit_SMF^-). Along with these groups, non-vitrified or fresh COCS, which exposed (nVit_SMF⁺) and non-exposed (nVit_SMF^-) to magnetic field, were also considered. Survival and viability rates and mitochondrial activity as well as ultrastructure of oocytes were examined by trypan blue Staining (TBS), Annexin-PI Staining, JC1 staining and transition electron microscopy, respectively. Following in vitro fertilization (IVF) and embryo development, gene expression was carried out through qRT-PCR at blastocyst (BL) stage. The survival rate in Vit_SMF⁺ and Vit_SMF^- decreased meaningfully in comparison with nVit_SMF^- (P < 0.05), but there was no significant difference between SMF⁺ and SMF^- groups. The mitochondrial activity in Vit_SMF^- was significantly reduced compared to the nVit_SMF^- group (P < 0.05), however its value in Vit_SMF⁺ returned to the control level. Ultrastructural study demonstrated that SMF could protect the COCs from cryoinjuries and reduced damaged features in ooplasm of the vitrified oocytes. There was no significant difference in fertilization rate. Although, BL formation was the highest rate in the Vit_SMF⁺ group, it was just substantially higher than the non-vitrified groups (P < 0.05). The significant changes of Oct4, Cdx2 and Nanog genes expression due to vitrification (Vit_SMF^-) or SMF (nVit_SMF⁺) treatments (P < 0.05) as compared to control (nVit_SMF^-), returned to the natural level after using SMF in vitrified derived blastocysts (Vit_SMF⁺). Totally based on the results, it is clear that static magnetic field improves mitochondrial potential activity and ultrastructure of mouse vitrified COCs. In addition, SMF enhances the embryo cleavage rate to blastocyst stage and modulates pluripotency in blastocyst embryos derived from vitrified COCs.

NADPH oxidase 5 activation; a novel approach to human sperm cryoinjury

Sperm cryopreservation leads to various structural and functional damages, some of which induce by oxidative stress. The reactive oxygen species (ROS) generates by mitochondria and membrane NADPH oxidases (NOXs). Among the NOXs, only NOX5 has been identified in the cell membrane of human sperm. This study was designed to clarify the possible role of NOX5 on sperm cryoinjury. Forty human semen samples were washed and randomly divided into fresh and cryopreserved groups. Each group was divided into 4 subgroups containing Ham's F10 (control), 0.1% DMSO (vehicle), 100 nM of PMA (phorbol 12-myristate 13-acetate) and 1 µM of DPI (diphenyleneiodonium), as NOX5 activator and inhibitor. The samples of cryopreserved groups were preserved in liquid nitrogen for 1 month. The sperm kinematics, membrane integrity, ROS production, apoptosis rate, mitochondrial membrane potential (MMP), intracellular ATP and calcium concentration [Ca²⁺]_i were evaluated. The percent of sperm with intact membrane and motile sperm reduced significantly after thawing (p ≤ 0.01). The ROS production (p ≤ 0.01) and the apoptotic rate increased, MMP dissipated, and the percentage of live cells with high [Ca²⁺]_i decreased significantly in the cryopreserved control group relative to the fresh control group. DPI, in contrast to PMA, improved sperm progressive motility (p ≤ 0.01), membrane integrity in fresh and cryopreserved groups and reduced the ROS amount in cryopreserved group (p ≤ 0.01). Apoptotic rate, [Ca²⁺]_i, ATP, and MMP did not change with DPI and PMA in cryopreserved groups. We conclude that NOX5 activity in fresh sperm is low, and it increases during cryopreservation. NOX5 inhibition improves the cryopreserved sperm quality.