Extending The Life-Span Of Frozen Sperm

Scientists in Japan have developed a cold preservation technology that keeps refrigerated mouse sperm alive for up to ten days.

AsianScientist (Dec. 13, 2017) – A team of researchers at Kumamoto University in Japan have succeeded in developing a refrigeration preservation technology that maintains viable mouse sperm for ten days. They published their method in Biology of Reproduction.

Many universities and pharmaceutical companies are engaged in research and development using genetically modified mice that have certain genes manipulated to reproduce human diseases. Since these mice are useful for tasks such as ascertaining the safety of drugs, or investigating the cause of a disease, they are frequently transported to laboratories around the world. It is common to transport live mice in special containers, but there is a risk that they might die due to stress during shipping, or escape due to mishandling or an accident. This is highly undesirable from the viewpoints of animal welfare and ecosystem preservation.

Refrigerated sperm transportation has been proposed as a method to replace the transportation of adult genetically modified mice. By performing in vitro fertilization with refrigerated sperm, it is possible to prepare a large number of genetically modified mice all at once. In other words, refrigerating and transporting the sperm of genetically modified mice solves the problems of live animal transportation.

In this study, the researchers conducted mutual transportation tests of refrigerated sperm between Kumamoto University in the south of Japan and Asahikawa Medical University in the north, and between Kumamoto University, Japan, and the University of California, Davis. However, the period during which the mouse sperm could be refrigerated and remain viable was limited to three days. After three days, the sperm were no longer able to fertilize eggs.

The researchers thus aimed to improve the low temperature tolerance of sperm by adding quercetin, which is an antioxidant contained in cold-hardy plants, and dimethylsulfoxide (DMSO), which is widely used as a cryoprotective substance, to a preservation solution. The two substances dramatically improved cold-preserved sperm motility and allowed its fertilizing ability to be maintained for ten days.

Using the refrigerated sperm, the researchers were able to fertilize an egg in vitro and produce a normal mouse pup. In addition, they investigated the function of sperm treated with quercetin and DMSO in detail and found that the activity of the energy-producing mitochondria was elevated. When the researchers observed the sperm with a fluorescence microscope, they found that quercetin accumulated in the middle of the sperm, where the mitochondria are located. The results suggest that quercetin may protect the mitochondria in sperm.

“This research makes it possible to transport genetically modified mice safely and easily to research organizations around the world,” said Dr. Toru Takeo of Kumamoto University who led the research. “We expect that this method will accelerate international collaborative research and contribute to the fields of medicine and life science research.”

The article can be found at: Yoshimoto et al. (2017) Dimethyl Sulfoxide and Quercetin Prolong the Survival, Motility, and Fertility of Cold-stored Mouse Sperm for 10 Days.


Source: Kumamoto University; Photo: Shutterstock.
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