induced pluripotent stem cell

An induced pluripotent stem cell, or iPSC, is an ordinary specialized adult cell that has been rewound back to a blank, embryo-like state. Take a fully committed cell — a bit of skin or blood, say — and switch a few master genes back on, and the cell forgets its job and reverts to behaving like a pluripotent stem cell. It is like resetting a device to its factory settings: the same hardware, wiped clean and ready to be configured into anything again.

The breakthrough came in 2006, when Shinya Yamanaka showed that introducing just a small set of reprogramming factors — the so-called Yamanaka factors — could reset a mature cell's identity. These factors flip the cell's internal control switches back toward the pattern seen in early development, reactivating the pluripotency program the cell had long since shut off. The result is a cell that, by every practical test, behaves like an embryonic stem cell.

The reason iPSCs caused such excitement is that they deliver pluripotency without an embryo, sidestepping the central ethical objection to embryonic stem cells. They can also be made from a specific patient's own cells, yielding pluripotent cells that are a genetic match and far less likely to be rejected. They have become indispensable for studying disease and screening drugs in a dish, though using them to grow safe transplant tissue is still an active, demanding area of research.