How are induced pluripotent stem cells made from adult skin or liver cells?

Induced pluripotent stem cells (iPS cells) are generated by reprogramming mature adult cells—such as skin or liver cells—back into a pluripotent, stem-like state. This process avoids the ethical concerns associated with using embryonic stem cells.123

To achieve this, researchers introduce specific regulatory genes into the nuclei of adult cells grown in cell culture. The most common method involves using viral vectors, such as retroviruses, to transport these genes into the cells. These genes encode transcription factors that are essential for maintaining pluripotency, including Oct-4, Sox-2, Klf-4, and Nanog. Once inside the nucleus, these factors reprogram the cell's genetic expression, allowing it to regain the capacity to differentiate into various cell types.132

Because retroviral delivery can integrate into the host genome and potentially cause tumors, scientists are exploring safer alternatives, such as plasmids or the direct delivery of proteins and modified RNAs. These reprogrammed cells are invaluable in regenerative medicine because they can be derived from a patient's own tissue, significantly reducing the risk of immune rejection during transplantation.132