Although there are few side by side comparisons directed at revealing subtle differences between ESCs and iPSCs, published results so far, largely confirm that irrespective of the path to pluripotency, the cells behave virtually similarly to each other. Nevertheless, some differences have been observed. The frequency of karyotypic abnormalities in iPSCs seems to be higher than in ESCs. Anecdotal evidence also suggests that teratomas from iPSCs appear less complex and more cystic. The frequency and extent of chimerism with mouse iPSCs is more limited and there appear biases depending on the cell of origin of the pluripotent population. More recently, differences between iPSCs and ESCs in gene expression have been reported [7], however, whether these differences are significant and wider than normal allelic differences remains to be seen.
