Induced pluripotent stem cells are generated by direct reprogramming of somatic cells with the introduction of defined transcription factors or other means. Clinical applications of induced pluripotent stem cells are the latest of stem cell therapy approaches due to overcoming problems associated with insufficient cells from conventional sources and immune rejections. In practice, this is restricted by 4 major barriers including the use of genetic manipulations for delivering the reprogramming factors, low efficiency of this process, slow kinetics of the direct reprogramming, and potential for tumor development. Here, we review the latest achievements in improving reprogramming efficiency by alternative strategies. These alternatives mainly involve the replacement of genetic reprogramming factors with small molecules or other factors.
