Nov. 20, 2007 -- Working independently, scientists in the U.S. and in Japanhave turned human skin cells back into embryo-likestem cells.
The reprogrammed adult cells become "truly pluripotent" stem cells-- that is, they can become any cell in the human body. Until now, onlyembryonic stem cells could do that trick. But unlike with embryonic stem cells,no embryo has to be destroyed to get these stem cell lines.
"Basically, what we are doing is trying to turn somatic cells from anadult body back into stem cells similar to embryonic stem cells,"University of Wisconsin researcher Junying Yu, PhD, says in a podcast madeavailable by the journal Science.
There is a catch. To reprogram the adult cells into what they call"induced pluripotent cells," both research teams had to useretroviruses as vectors to carry new genes into the cell nucleus. Once there,the retroviruses become part of the cell's genetic code. These retrovirusescould cause deadly mutations or cancers in patients treated with the newlycreated stem cells.
"It is important to understand, however, that before the cells can beused in the clinic, additional work is required to avoid vectors that integrateinto the genome, potentially introducing mutations at the insertion site,"warn Yu and colleagues, in one of the two reports simultaneously announcing theresults.
But both research teams are highly optimistic that science soon will leapthis hurdle.
"Once the safety issue is overcome, human-induced pluripotent cellsshould be applicable in regenerative medicine," Kyoto University researcherKazutoshi Takahashi and colleagues note in their report.
Until that breakthrough occurs, the stem cells will be of enormous value indrug development and in understanding human disease.
Not True Embryonic Stem Cells
Both research teams note that the induced pluripotent stem cells, or iPScells, are not exactly the same as embryonic stem cells. Precisely howdifferent they are remains a question. Regardless of the difference, thefinding may represent a breakthrough in the ethical debate over the use ofembryonic stem cells, says medical ethicist R. Alta Charo, JD, of theUniversity of Wisconsin-Madison.
"This is a method for creating a stem cell line without ever having towork through, at any stage, an entity that is a viable embryo," Charo saysin a news release. "Therefore, you manage to avoid many of those debateswith the right-to-life community."
The two research teams used different techniques. Both used retroviruses toinsert four genes into more mature cells, but only two of these genes were thesame. The group working in Japan used skin cells from the face of a 36-year-oldwoman and from the connective tissue of a 69-year-old man. The group working inthe U.S. used cells from a fetus and from a newborn child, although Yu saysthey are well on the way to using cells from human adults.
Both teams are building on mouse studies announced last year by the leaderof the Japanese team, Shinya Yamanaka, MD, PhD, of Kyoto University. The leaderof the U.S. team is James A. Thompson, DVM, PhD, of the University ofWisconsin-Madison.
Takahashi, Yamanaka, and colleagues report their findings in the Nov. 20online edition of the journal Cell. Yu, Thompson, and colleagues reporttheir findings in the Nov. 22 online edition of the journal ScienceExpress.