Induced pluripotent stem cells, from generation to application: review article

Embryonic stem cells are pluripotent stem cells which have the ability to indefinitely self-renew and differentiate into all differentiated cells of the body. Regarding their two main properties (unlimited self-renewal and multi-lineage differentiation), these cells have various biomedical applications in basic research and cell based therapy. Because the transplantation of differentiated cells that are derived from embryonic stem cells is allogenic, they face the problem of immune rejection following the transplantation of embryonic stem cell-derived cells into patients. In 2006, researchers from Japan reported the derivation of a new type of pluripotent stem cells which could overcome the problem of immune rejection that is associated with the application of embryonic stem cells. They designated these cells as induced pluripotent stem (iPS) cells, because their production was ‘induced’ from differentiated somatic cells using a combination of four embryonic stem cell-associated transcription factors. Importantly, these pluripotent stem cells exhibit all the key features of embryonic stem cells including unlimited self-renewal and multi-lineage differentiation potential, and can pass the most stringent test of pluripotency which is known as the tetraploid (4n) complementation. Hence, in addition to bypassing the problem of immune rejection, iPS cells have all of the potential applications of embryonic stem cells, including in developmental studies, toxicology research, drug discovery and disease modeling. Also, considering that they could be generated from patient’s own cells, iPS cells hold great promise in the future of patient-specific cell replacement therapies using pluripotent stem cells. In this review article, we will present a comprehensive review on the how and why of the generation of iPS cell from somatic cells of the body and discuss how they should be characterized in terms of morphologically, pluripotent stem cell behavior, and the molecular signature. In addition, their medical applications as well as some of the considerations and future challenges in their use will be discussed.