Generation of rat and human induced pluripotent stem cells by combining genetic reprogramming and chemical inhibitors.

(Cell Stem Cell 4, 16–19; January 9, 2009)In our recent article, we unfortunately misquoted the findings in a recent study by Ying et al. (2008)xThe ground state of embryonic stem cell self-renewal. Ying, Q.-L., Wray, J., Nichols, J., Batlle-Morera, L., Doble, B., Woodgett, J., Cohen, P., and Smith, A. Nature. 2008; 453: 519–523Crossref | PubMed | Scopus (1294)See all ReferencesYing et al. (2008). When describing previous work using combination of the MEK inhibitor PD0325901 and the GSK3b inhibitor CHIR99021, our statement “Recent studies demonstrated that addition of the FGFR inhibitor PD173074 to the above cocktail is sufficient to maintain mESC pluripotency in the absence of LIF (Ying et al., 2008xThe ground state of embryonic stem cell self-renewal. Ying, Q.-L., Wray, J., Nichols, J., Batlle-Morera, L., Doble, B., Woodgett, J., Cohen, P., and Smith, A. Nature. 2008; 453: 519–523Crossref | PubMed | Scopus (1294)See all ReferencesYing et al., 2008).” was not accurate. Ying et al., in fact, used PD0325901 to replace PD1730474 and demonstrated maintenance of mESCs in the absence of LIF with these two factors only.The corrected section reads “Indeed, after serial passages, the growth of putative riPSCs treated with only PD0325901 and CHIR99021 declined, and the culture deteriorated due to the expansion of differentiated cells, although recent studies demonstrated that this combination of inhibitors can be used to maintain mESC self-renewal in the absence of LIF (Ying et al., 2008xThe ground state of embryonic stem cell self-renewal. Ying, Q.-L., Wray, J., Nichols, J., Batlle-Morera, L., Doble, B., Woodgett, J., Cohen, P., and Smith, A. Nature. 2008; 453: 519–523Crossref | PubMed | Scopus (1294)See all ReferencesYing et al., 2008). Because the TGFβ/Activin A/Nodal signaling cascade is essential to maintain undifferentiated hESCs and EpiSCs, but dispensable for mESC self-renewal, we tested whether the addition of an inhibitor of the type 1 TGFβ receptor, ALK5 (A-83-01), could help stabilize our riPSC cultures.”In addition, we omitted to mention that while our study was under review, Silva et al. (2008)xPromotion of Reprogramming to Ground State Pluripotency by Signal Inhibition. Silva, J., Barrandon, O., Nichols, J., Kawaguchi, J., Theunissen, T.W., and Smith, A. PLoS Biol. 2008; 6: 2237–2247Crossref | Scopus (456)See all ReferencesSilva et al. (2008) also published the use of these two inhibitors in the generation and propagation of mouse iPSCs.We apologize for any confusion caused.