New Techniques in the Generation of Induced Pluripotent Stem Cells

Abstract

Pluripotent stem cells have the ability to differentiate into cells of the three primary germ layer lineages, ectoderm, mesoderm and endoderm. The most studied type of pluripotent stem cells are embryonic stem cells (ESC), cells derived from the inner cell mass of embryos at the blastocyst stage of development (Evans and Kaufman, 1981; Martin, 1981; Thomson et al., 1998). The pluripotent property of human embryonic stem cells (hESC) makes them useful for the development of cellular therapies to replace diseased or degenerated cells in the body. Moreover, hESC also possess the ability to propagate indefinitely in vitro while maintaining a normal karyotype, and thus can provide an unlimited source of cells for the development of cell replacement therapies (Pera et al., 2000). However, one of the major hurdles in hESC research has been the ethical implications of using stem cells derived from embryos. Furthermore, generation of patient-specific stem cell lines may overcome some of the issues associated with immuno-compatibility in cell replacement therapy. The breakthrough studies conducted by Shinya Yamanaka’s group demonstrated direct reprogramming of mouse or human fibroblasts back to pluripotent cells, creating so-called induced pluripotent stem cells (iPSC) (Takahashi et al., 2007; Takahashi and Yamanaka, 2006). Studies of iPSC revolutionized stem cell research by creating a more reproducible method to generate sufficient amounts of patient-specific pluripotent cells and bypassing the ethical implications surrounding research utilizing human embryos. iPSC also provide an alternative approach to generate disease-specific lines for mechanistic studies in disease modeling, as well as high throughput screening for drug discovery or toxicology studies (Amabile and Meissner, 2009). As the area of iPSC research is rapidly evolving, this review aims to summarize and discuss the current techniques used for the generation of iPSC.