Induced pluripotent stem cell

A stem cell made by reprogramming an adult cell, such as a skin or blood cell, back to an embryo-like state that can become most cell types.

• Switching on four genes, the Yamanaka factors, resets which genes are active; the 2006 discovery won the 2012 Nobel Prize.
• Because they come from the patient, the tissues grown from them may avoid immune rejection, and they sidestep the ethics of embryonic stem cells.
• Researchers grow a patient's own neurons or heart cells to study disease and test drugs; transplant trials include Parkinson's and eye disease.
• Derived cells are often immature, and leftover unconverted stem cells could form tumours, so purity is a key safety test.