Thinking outside the liver: Induced pluripotent stem cells for hepatic applications

Table 1 New approaches to reprogramming of differentiated cells to a pluripotent state

Method	Results of reprogramming	Drawbacks	Ref.
Transfer of the nucleus from a somatic cell to an enucleated oocyte	The somatic cell nucleus is reprogrammed in the oocyte, and a whole organism develops as a result. Patient-specific hESCs can be derived	Low efficiency. Developmental abnormalities in cloned animals. Ethical and legal restrictions	[24-28]
Fusion of ESCs with differentiated cells	Hybrids of differentiated cells and ESCs display all properties of pluripotent cells	Cell hybrids lack a normal diploid chromosome set	[29,30]
Reprogramming of somatic cells to a pluripotent state can be generated by the ectopic expression of 4 transcription factors, Oct4, Klf4, Sox2 and c-Myc	Somatic cells regain a pluripotent state and become similar in properties to ESCs	Low efficiency of iPSC derivation. Viral integration. Tumor formation	[7]

ESCs: Embryonic stem cells; hESCs: Human embryonic stem cells; iPSC: Induced pluripotent stem cell; Oct: Octamer-binding transcription factor; Sox2: SRY box-containing gene 2; Klf4: Kruppel-like factor 4.