Not less than 75 mouse clones have been made.
Japanese scientists have produced mouse clones using freeze-dried cells, a technique they hope to one day use for species conservation by overcoming the challenges posed by biobanks.
Such facilities have sprung up around the world to conserve samples of endangered species, with the goal of ensuring their survival through cloning.
These samples, usually sperm or egg cells, are often cryopreserved in liquid nitrogen or at very low temperatures, processes that can be expensive and prone to power failures.
Researchers at Yamanashi University have sought to avoid these pitfalls through freeze-drying – which involves removing all of the water from a body by drying – somatic cells. That is, all those that are not related to sperm or oocytes.
They freeze-dried cells taken from the tails of mice or near immature oocytes from females. Freeze-drying killed the cells and damaged their DNA, but they could be used to create clones of blastocysts, an assembly of cells that develop into an embryo.
They then extracted stem cell lines from it, which made it possible to produce 75 mouse clones. One of them, Dorami, survived a year and nine months. The team also successfully bred nine females and three cloned males with normal mice.
The individuals were found to be largely healthy, if not a line obtained from male cells that produced only females. The fertility of the cloned mice was also found to be lower.
We believe we will be able to reduce abnormalities and increase fertility by researching protective freeze-drying agents and improving drying techniques, Teruhiko Wakayama, who contributed to the research, told AFP. published in Nature Communications.
The success rate of the technique, at just 0.02%, is still well below that of cryopreservation, or very low temperature, which ranges from 2% to 5%. But Mr. Wakayama, who defends a breakthrough thanks to this research, recalls that it remains innovative: the one that allowed the cloning of Dolly, the first sheep cloned in 1996, took 200 attempts.
Ultimately, this technique could make it possible to economically and safely preserve genetic material from around the world, Wakayama said. A considerable asset for developing countries.
The team, a pioneer in freeze-drying, sent freeze-dried sperm from mice to the International Space Station. The latter returned healthy after six years in space and, once rehydrated, produced young mice.