In 2006, Japanese scientist Shinya Yamanaka found a way to change skin cells into special cells. These iPS cells can become many kinds of cells, like heart or brain cells.

Doctors hope to use them to replace cells lost to illness. In a small study, seven patients with Parkinson's disease received cells made from iPS cells. In 2026, Japan approved the first iPS cell treatments, but with conditions.

For a long time, scientists believed that once a cell became a skin cell, it could never become anything else. In 2006, Shinya Yamanaka and Kazutoshi Takahashi proved this wrong. By adding just four genes to mouse skin cells, they created cells that could turn into many different types of tissue. They succeeded with human cells in 2007, and Yamanaka won the Nobel Prize in 2012.

Because iPS cells do not require fertilized eggs, they raise fewer ethical problems. In 2025, a Kyoto University team reported that cells made from iPS cells were transplanted into the brains of seven Parkinson's patients without causing tumors. In 2026, Japan gave conditional approval with a time limit to two iPS-based products, but their effectiveness still needs to be confirmed.

Until 2006, cell specialization was thought to run in one direction only. A skin cell, once specialized, could never go back to an earlier, more flexible state. That year, Yamanaka and Takahashi reported in Cell that adding just four genes to mouse fibroblasts produced pluripotent cells able to develop into many tissue types. Human cells followed in 2007, and Yamanaka shared the 2012 Nobel Prize.

Because iPS cells can be made from a patient's or donor's blood or skin instead of from embryos, they avoid many ethical objections. Clinical research began in 2014 with a retinal cell transplant for macular degeneration and has advanced steadily. In 2025, a Kyoto University team reported in Nature that it had transplanted dopamine-producing precursor cells made from iPS cells into seven Parkinson's patients.

The cells survived and produced dopamine, no tumors or serious side effects appeared, and four of the six patients evaluated improved off-medication motor scores. With no control group and few patients, the trial cannot rule out a placebo effect. In March 2026, Japan gave conditional, time-limited approval to two iPS-based products, for Parkinson's disease and severe heart failure. Their effectiveness has to be confirmed after launch, or the approval may lapse.