Two Supporting Factors Greatly Improve the Efficiency of Human iPSC Generation

Cell stem cell (Impact Factor: 22.27). 12/2008; 3(5):475-9. DOI: 10.1016/j.stem.2008.10.002
Source: PubMed


Human fibroblasts can be induced into pluripotent stem cells (iPSCs), but the reprogramming efficiency is quite low. Here, we screened a panel of candidate factors in the presence of OCT4, SOX2, KLF4, and c-MYC in an effort to improve the reprogramming efficiency from human adult fibroblasts. We found that p53 siRNA and UTF1 enhanced the efficiency of iPSC generation up to 100-fold, even when the oncogene c-MYC was removed from the combinations.

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Available from: Chun Liu, Jul 15, 2014
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    • "Importantly, the somatic cell is not a tabula rasa and expresses genes that antagonize reprogramming, as has been shown for tumor suppressors (p53, INK4a/ARF, LATS2) (Kawamura et al., 2009; Qin et al., 2012; Zhao et al., 2008) and H3K9 methyltransferases (SETDB1, SUV39H, EHMT2) (Chen et al., 2013). In addition, focused RNAi screens have revealed other pathways that act as barriers to reprogramming, such as TGF-b signaling (Samavarchi-Tehrani et al., 2010), H3K79 methylation by DOT1L (Onder et al., 2012), or protein ubiquitination (Buckley et al., 2012). "
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    ABSTRACT: Reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) holds enormous promise for regenerative medicine. To elucidate endogenous barriers limiting this process, we systematically dissected human cellular reprogramming by combining a genome-wide RNAi screen, innovative computational methods, extensive single-hit validation, and mechanistic investigation of relevant pathways and networks. We identify reprogramming barriers, including genes involved in transcription, chromatin regulation, ubiquitination, dephosphorylation, vesicular transport, and cell adhesion. Specific a disintegrin and metalloproteinase (ADAM) proteins inhibit reprogramming, and the disintegrin domain of ADAM29 is necessary and sufficient for this function. Clathrin-mediated endocytosis can be targeted with small molecules and opposes reprogramming by positively regulating TGF-β signaling. Genetic interaction studies of endocytosis or ubiquitination reveal that barrier pathways can act in linear, parallel, or feedforward loop architectures to antagonize reprogramming. These results provide a global view of barriers to human cellular reprogramming.
    Cell 07/2014; 158(2):449-61. DOI:10.1016/j.cell.2014.05.040 · 32.24 Impact Factor
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    • "In addition, activated tumor suppressor protein P53 positively correlates with FAS expression levels [37]–[40] and vice versa. Importantly, inhibition of P53 has been shown to enhance reprogramming efficiencies [41]. It would thus be interesting to investigate, whether FAS downregulation actively promotes reprogramming or is a consequence of negative regulation by OCT4 and lacking upregulation by P53. "
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    ABSTRACT: Cellular reprogramming of somatic cells into induced pluripotent stem cells (iPSC) opens up new avenues for basic research and regenerative medicine. However, the low efficiency of the procedure remains a major limitation. To identify iPSC, many studies to date relied on the activation of pluripotency-associated transcription factors. Such strategies are either retrospective or depend on genetically modified reporter cells. We aimed at identifying naturally occurring surface proteins in a systematic approach, focusing on antibody-targeted markers to enable live-cell identification and selective isolation. We tested 170 antibodies for differential expression between mouse embryonic fibroblasts (MEF) and mouse pluripotent stem cells (PSC). Differentially expressed markers were evaluated for their ability to identify and isolate iPSC in reprogramming cultures. Epithelial cell adhesion molecule (EPCAM) and stage-specific embryonic antigen 1 (SSEA1) were upregulated early during reprogramming and enabled enrichment of OCT4 expressing cells by magnetic cell sorting. Downregulation of somatic marker FAS was equally suitable to enrich OCT4 expressing cells, which has not been described so far. Furthermore, FAS downregulation correlated with viral transgene silencing. Finally, using the marker SSEA-1 we exemplified that magnetic separation enables the establishment of bona fide iPSC and propose strategies to enrich iPSC from a variety of human source tissues.
    PLoS ONE 07/2014; 9(7):e102171. DOI:10.1371/journal.pone.0102171 · 3.23 Impact Factor
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    • "The reprogramming is slower and stochastic, suggesting the existence of a barrier that limits its efficiency. To increase the efficiency of reprogramming, the repression of RIS or reprogramming-induced apoptosis is definitely required at the late stage followed by a decrease in the expression of p16INK4a, p21CIP1, and p53 by hypoxic or other conditions, which are necessary for full reprogramming [43,45-47,67,68] (Figure 1). "
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    ABSTRACT: Because of their pluripotent characteristics, human induced pluripotent stem cells (iPSCs) possess great potential for therapeutic application and for the study of degenerative disorders. These cells are generated from normal somatic cells, multipotent stem cells, or cancer cells. They express embryonic stem cell markers, such as OCT4, SOX2, NANOG, SSEA-3, SSEA-4, and REX1, and can differentiate into all adult tissue types, both in vitro and in vivo. However, some of the pluripotency-promoting factors have been implicated in tumorigenesis. Here, we describe the merits of tumor suppresser genes as reprogramming factors for the generation of iPSCs without tumorigenic activity. The initial step of reprogramming is induction of the exogenous pluripotent factors to generate the oxidative stress that leads to senescence by DNA damage and metabolic stresses, thus inducing the expression of tumor suppressor genes such as p21CIP1 and p16INK4a through the activation of p53 to be the pre-induced pluripotent stem cells (pre-iPSCs). The later stage includes overcoming the barrier of reprogramming-induced senescence or cell-cycle arrest by shutting off the function of these tumor suppressor genes, followed by the induction of endogenous stemness genes for the full commitment of iPSCs (full-iPSCs). Thus, the reactive oxygen species (ROS) produced by oxidative stress might be critical for the induction of endogenous reprogramming-factor genes via epigenetic changes or antioxidant reactions. We also discuss the critical role of tumor suppressor genes in the evaluation of the tumorigenicity of human cancer cell-derived pluripotent stem cells, and describe how to overcome their tumorigenic properties for application in stem cell therapy in the field of regenerative medicine.
    Stem Cell Research & Therapy 04/2014; 5(2):58. DOI:10.1186/scrt447 · 3.37 Impact Factor
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