Lab rats / mice

File photo of lab rats not involved in study. (© Gorodenkoff -

YAMANASHI, Japan — Scientists have successfully cloned mice using cells that were freeze dried for up to nine months. They were all born perfectly normal and healthy and went on to have offspring of their own. The breakthrough could help feed growing populations — and save endangered animals from extinction.

Researchers from the University of Yamanashi in Japan used “somatic cells” in the mice-cloning experiment. These cells are found in any organ or tissue not involved in reproduction. They can be stored at -30 degrees centigrade. Sperm needs -196 degrees, which requires liquid nitrogen and is costly and inefficient.

“Whole animal cloning could be used to secure biodiversity and rescue threatened species. However, current bio-banking methods rely on ultra-low temperature storage, which is expensive and vulnerable to power outages or other problems,” the authors explain in a statement per South West News Service. “Here, we show freeze-dried somatic cells can produce healthy, fertile clones, suggesting this technique may be important for the establishment of alternative, cheaper and safer liquid nitrogen-free bio-banking solutions.”

It should work for much larger animals, from cattle and other livestock to elephants and big cats.

The study, published in Nature Communications is a major step forward in preserving genetic material. Recent advances have focused on freeze-dried sperm cells which are more vulnerable to damage. So Prof Wakayama and colleagues turned to hardier somatic cells. They died during freeze-drying and were then “brought back to life.”

A technique called somatic cell nuclear transfer spawned early embryos, or blastocysts, yielding stable stem cell lines. Dolly the Sheep was cloned in 1996 using the same process. It takes a somatic cell, such as a skin cell, and moves its DNA to an egg cell with its nucleus removed. The donor cells had a high success rate of more than 5 percent, generating healthy female and male pups.

In further experiments, a dozen of the cloned mice — nine females and three males — were selected for mating with peers that had been born naturally.

“All females delivered a litter of mice, indicating normal fertility of the cloned animals,” the authors tell SWNS. “Freeze-drying causes more DNA damage than storing cells via current methods. But the cloning rate achieved indicates it may be an alternative. This is especially true when cost and long-term security are the main concerns. It could provide a viable method for the storage of genetic material from any animal in a safe and low cost way.”

South West News Service writer Mark Waghorn contributed to this report.

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