Increasing evidence suggests that iPSC reprogramming of somatic cells into the embryo-like state largely resets their epigenetic state and either permanently deletes or temporarily conceals any memory of their age of origin. To test this paradigm in the context of human aging, we obtained skin fibroblasts from 19 individuals ranging in age from 0 to 89 years (Table S1) and reprogrammed 16 lines into iPSCs by overexpression of the four Yamanaka factors (Figure 1A) (Takahashi et al., 2007). Clonally derived iPSCs showed typical morphologies of human pluripotent cells and nuclear expression of Nanog (Figure 1B); they were analyzed by G-banding to be karyotypically normal (Figure 1C). All iPSC lines possessed an expression profile typical of pluripotent stem cells, with Lin28A/B, MycN, Nanog, Tert, Oct4, Nodal, Dppa2/4, and Otx2 all being more than 1,0003× upregulated as compared to fibroblasts (Figure 1D; Table S2). To investigate the extent to which iPSCs can retain the aging signatures of their donors, we performed high-throughput whole transcriptome RNA sequencing (RNA-seq) and compared the gene expression patterns of old and young fibroblasts and of derived iPSCs.
