Induced pluripotent stem cells in regenerative medicine: an argument for continued research on human embryonic stem cells

Human embryonic stem cells (ESCs) can be induced to differentiate into a wide range of tissues that soon could be used for therapeutic applications in regenerative medicine. Despite their developmental potential, sources used to generate human ESC lines raise serious ethical concerns, which recently prompted efforts to reprogram somatic cells back to a pluripotent state. These efforts resulted in the generation of induced pluripotent stem (iPS) cells that are functionally similar to ESCs. However, the genetic manipulations required to generate iPS cells may complicate their growth and developmental characteristics, which poses serious problems in predicting how they will behave when used for tissue-regenerative purposes. In this article we summarize the recently developed methodologies used to generate iPS cells, including those that minimize their genetic manipulation, and discuss several important complicating features of iPS cells that may compromise their future use for therapies in regenerative medicine.