PSCs

Pluripotent stem cells (PSCs) are cells capable of indefinite self-renewal and differentiation into cell types from the three germ layers: endoderm, mesoderm, and ectoderm. In vivo they typically do not form placental or other extraembryonic tissues, a property that distinguishes them from totipotent cells.

The main classes of PSCs are embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). ESCs are derived from the inner cell mass of blastocysts, typically from surplus embryos used in assisted reproduction, and are inherently pluripotent. iPSCs are produced by reprogramming differentiated somatic cells through transcription factors to revert to a pluripotent state, enabling patient- or donor-specific cell lines.

PSCs are used in basic biology to study development and gene function, and in applied research for disease modeling, drug screening, and toxicology tests. They are also explored for regenerative medicine and cell therapies to replace damaged tissues, and as a platform for discovering and testing new treatments.

Clinical translation faces several challenges, including the risk of tumor formation if undifferentiated cells are transplanted, immune compatibility concerns, and the need for robust, standardized methods to direct differentiation and scale production. Ethical, legal, and regulatory considerations differ by jurisdiction, particularly for ESCs, reflecting debates over embryo use and consent.

Notable milestones include the isolation of the first human ESC line in 1998 and the development of iPSCs in 2006–2007, which provided an alternative source of pluripotent cells without the use of embryos.