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

SIMPLE SUMMARY: Understanding freezing is essential for stable cryopreservation of sperm. In the freezing process, ice crystal is developed from a change of matter from liquid water to solid water. Unfortunately, they tend to make damage of membrane in frozen sperm. From a perspective, sperm membrane damage due to ice crystal formation, magnetized freezing water that has easy supercooling, and the construction of smaller ice crystals because weaken the hydrogen bonds between the water molecules also has an infinite potential to cryopreserve sperm. Here, we applied the magnetization technique for making of freezing extender, and the extenders were used in the freezing process in sperm cryopreservation. As a result, sperm membrane damage was reduced in frozen sperm by a magnetized freezing extender, and we determined that in vitro fertility of frozen sperm by magnetized extender was improved. In conclusion, the magnetization technique would be useful for sperm cryopreservation. Furthermore, the study suggests that the technique has great potential for storing frozen material for biological aspects. ABSTRACT: 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.