deacetylase (HDAC) inhibitors (such as hydroxamic acid (SAHA), trichostatin A (TSA), and valproic acid (VPA)) (Huangfu et al., 2008). The delivery of the OKSM transcription factors into mouse or human fibroblasts is achieved using different viral and non-viral constructs, as well as integrative and non-integrative systems approaches, the latter of which have presented major problems for iPSCs generation. Four main groups of different non-integrative approaches are available: integration-defective viral delivery, episomal delivery, RNA delivery and protein delivery (González et al., 2011). There is no best reprogramming strategy that can be used to fit all purposes. The choice of the strategy highly depends on the purpose of the research; whether it focuses on understanding the mechanisms of reprogramming or on generating clinically relevant iPSCs. Integrative methods with lentiviruses can be sufficient for the former use while non-integrative approaches should be used for the latter to limit genomic modifications.
