induced pluripotent stem cell
/ in-DOOST ploor-IP-uh-tent STEM sel /
Imagine telling a fully trained, retired surgeon to forget their specialty and go back to being a fresh medical student who could still choose any field. For a long time this seemed impossible for cells — once specialized, a cell stayed that way. Induced pluripotent stem cells are the astonishing result of doing exactly that to a cell: taking an ordinary mature cell and resetting it to a pluripotent, undecided state.
Precisely, an induced pluripotent stem cell (iPSC) is a pluripotent stem cell made by reprogramming an ordinary body cell — typically a skin or blood cell — usually by forcing it to make a small set of master transcription factors (the classic four are often called the Yamanaka factors). These factors switch the cell's gene-expression program back to an embryonic-stem-cell-like state, so the cell regains the ability to self-renew and to become any body cell type.
iPSCs matter enormously because they sidestep two big problems of embryonic stem cells: they need no embryo, and they can be made from a patient's own cells, reducing immune rejection. They are already powerful for modeling disease and screening drugs in a dish. But honesty is essential: turning iPSCs into safe, pure, mature therapies is hard, leftover undifferentiated cells can form tumors, and most clinical use is still experimental, not routine.
A researcher can take a small skin biopsy from a patient with a heart disorder, reprogram the skin cells into iPSCs, then turn those into beating heart cells in a dish — recreating the patient's diseased cells to study and test drugs without touching the patient's actual heart.
iPSCs for disease modeling: a patient's skin becomes their heart cells in a dish.
The 2006 discovery that a few transcription factors can reprogram an adult cell to pluripotency overturned the belief that differentiation is irreversible — but iPSCs are still mostly a research and drug-testing tool, not a routine cure.