Twenty Years After His Discovery, Yamanaka's Reprogrammed Cells Reach Patients — and Now Target Aging

It has been 20 years since Shinya Yamanaka published a paper showing that any adult cell in the body could be reprogrammed back to an embryo-like state, capable of developing into any of the body's other cell types. The discovery, which earned Yamanaka the 2012 Nobel Prize in Physiology or Medicine, is now moving into the clinic: this year, the first treatments based on the 2006 discovery became available to some patients.

"I can't believe it's been 20 years already," Yamanaka said in a recent interview at the Center for iPS Cell Research and Application (CiRA) at Kyoto University, which he helped create and directed for 12 years. "And I would say, so far, so good. The technology has grown, so now we are seeing medical applications of this on a small scale."

Before Yamanaka's work, scientists believed human cells could only develop in one direction, maturing from embryonic stem cells into specialized adult cells such as skin or blood cells, never the reverse. Yamanaka's approach was different: rather than starting with embryonic stem cells, he began with mature, specialized cells and searched for a way to revert them to an embryo-like state, drawing on earlier work by British biologist John Gurdon, who showed in the 1960s that a cell from a developed tadpole still held the genetic instructions to become a new frog, and by Scottish embryologist Ian Wilmut, who cloned a sheep from a mature adult cell in 1996.

That work created induced pluripotent stem cells, or iPS cells — adult cells reprogrammed to behave like embryonic ones, opening new ways of treating disease by replacing failing cells. Researchers are now studying whether cells need to be reprogrammed all the way back to a blank embryonic state, or whether partially reprogramming older cells could be enough to rejuvenate them and slow some aging processes.

"It's a very active area of research," Yamanaka said. "And I think partial reprogramming is a very powerful potential way to live healthier and longer."