fibroblasts as the starting somatic cell type since fibroblasts were also used for reprogramming mouse cells earlier. In addition, fibroblasts are easily cultured and expanded. Nevertheless, some disadvantages of reprogramming fibroblasts such as their relatively low reprogramming efficiency and especially the need of uncomfortable biopsies have led to a search for other cell sources. The molecular properties of the different cell types leading to variations in the reprogramming efficiency have been reviewed in [14]. Publications describe, amongst others, three relatively easy to obtain cell types, that is, blood cells [15], exfoliated renal tubular epithelial cells, obtained from urine [16], and keratinocytes from plucked hair [17]. In particular, keratinocytes seem to be a promising material for reprogramming because they combine the benefits of a noninvasive procedure, an easy way of transport, and a high reprogramming efficiency.
