New Kyoto U. method creates safer iPS cells

Written by changthai11 on Saturday, October 11th, 2008

OSAKA–A Kyoto University research group led by Prof. Shinya Yamanaka has successfully produced induced pluripotent stem (iPS) cells in mice without using viruses, in a breakthrough method that results in iPS cells that are considerably safer than those produced with the use of viruses.

The finding is expected to boost research into regenerative medicine using iPS cells, which can be developed into any type of cell.

In terms of iPS cell production, the new method is only one to 10 percent as efficient as a different method involving retroviruses, but iPS cells produced by the retrovirus method are thought prone to cause cancer.

The group’s findings will be published Friday in the online edition of Science magazine.

The group has previously produced iPS cells by infecting human and mouse skin cells with retroviruses embedded with three or four genes. But this method heightens the risk of cancer in the skin cells, due to chromosome damage that can be inflicted by the viruses.

In researching the new method, the group focused on plasmids, circular DNA molecules that are absorbed by skin cells within a couple of days, with no damage to chromosomes.

The group embedded three genes into a single plasmid, and a fourth gene into another plasmid. These plasmids were wrapped in lipid membranes, and then inserted into skin cells of in utero mice. The lipid membranes then integrated with the natural membranes of the skin cells.

Yamanaka said: “Plasmids are safe and cheap, because they can be produced in large quantities in a laboratory, and preserved in a frozen state. It is considered a new generation of iPS cells.”