Japanese research team succeeds in the world's first experiment to create cloned mice from 'freeze-dried somatic cells'
Freeze-drying is a technology that quickly freezes an object at about -30 degrees Celsius, creates a vacuum to remove water, and dries it. Today, it is applied to the production of preserved foods and space foods. It was newly reported that a research team at the University of Yamanashi succeeded in an experiment to produce cloned mice from 'somatic cells that had been freeze-dried and stored for up to 9 months.'
Healthy cloned offspring derived from freeze-dried somatic cells | Nature Communications
Succeeded in producing cloned mice from freeze-dried somatic cells-as the ultimate preservation method of genetic resources-.pdf
(PDF file) https://www.yamanashi.ac.jp/wp-content/uploads/2022/06/20220630pr.pdf
Animals Have Been Cloned From Freeze-Dried Skin Cells in a Scientific First
Conserving the genetic resources of plants and animals is important for maintaining biodiversity from disasters and climate change. However, the method of storing animal eggs and sperms using existing liquid nitrogen is difficult and expensive, and there is a problem that if the supply of liquid nitrogen is stopped due to a large-scale earthquake etc., it will melt and become unusable. ..
Therefore, the research team at the University of Yamanashi has been developing storage technology using freeze-drying, which is cheaper, for more than 20 years. We have already succeeded in freeze-drying sperm cells, and succeeded in producing pups from freeze-dried sperm stored in a desk drawer for over a year and freeze-dried sperm stored at the International Space Station for about 6 years. was doing.
However, sperm cannot be collected from old or young individuals or infertile individuals, and it is difficult to collect eggs from female individuals. Therefore, the research team of Assistant Professor Kiyoka Wakayama , who belongs to the Developmental Engineering Research Center of the University of Yamanashi, worked on the research of freeze-drying somatic cells that can be collected from any individual and creating clones. Almost a quarter of a century has passed since the successful freeze-dry storage of sperm, but there have been no cases where cells other than sperm have been successfully freeze-dried.
First, the research team collected cumulus cells around the egg from female mice and treated them with trehalose or epigallocatechin (gallocatechol) as a cryoprotectant. After that, the cells were freeze-dried and stored at -30 degrees Celsius for up to 9 months.
After the end of the storage period, water was added to the stored cumulus cells to restore them, and the degree of DNA damage was examined, or the cell nuclei were transplanted into egg cells to examine the incidence of cloned embryos. As a result, the incidence of blastocysts was only 0.1% when trehalose was used, but the incidence improved to 2.1% when epigallocatechin was used. As a result of culturing these cloned embryos in an embryonic stem cell (ES cell) establishment medium for 2 weeks, the research team said that they succeeded in establishing cloned ES cells at a rate of about 1% from freeze-dried oval cells. Is reporting.
Subsequently, fibroblasts collected from male and female tails were treated with epigallocatechin, which was confirmed to be effective in cumulus cell experiments, and stored freeze-dried to attempt to establish cloned ES cells. As a result, 1 to 2% of all mice could be established as cloned ES cells regardless of gender.
Finally, the research team challenged the production of cloned mice by performing nuclear transplantation using the established cloned ES cells as donors. As a result, we succeeded in producing a total of 75 cloned mice with a probability of 0.2 to 5% (about 2% on average). The first cloned mouse was named 'Dorami', and it was confirmed that the fertility as a female was normal and that it survived for 676 days and the life span was within the normal range. All other cloned mice examined had normal fertility.
The black individual on the left side of the image below is 'Dorami'.
by National University Corporation Yamanashi University
In this study, the success rate of the step of establishing cloned ES cells from somatic cells was about 1%, and the success rate of the step of creating cloned mice from cloned ES cells was about 2%. The research team points out that the success rate of producing is only 0.02%. This success rate is lower than the success rate (0.4%) of the sheep dolly , the first cloned mammal, so it is necessary to improve the success rate in the future to gain trust.
Also, this time, freeze-dried cells were stored in a freezer at -30 degrees Celsius, but it is necessary to enable storage at room temperature so that they can be safely stored even if the power supply is stopped due to a major disaster or the like. .. In this regard, freeze-dried somatic cells have already been stored at room temperature, so it is believed that freeze-dried somatic cells can also be stored at room temperature.
Furthermore, it seems that a case occurred in which the Y chromosome was lost from the freeze-dried male somatic cells in only one case, and many female cloned mice were born. Recreating this also showed the possibility of cloning females from endangered species that only survived males to keep the species alive, the researchers said.