Mechanistic insights into reprogramming to induced pluripotency

Department of Biological Chemistry, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California 90024, USA.
Journal of Cellular Physiology (Impact Factor: 3.87). 04/2011; 226(4):868-78. DOI: 10.1002/jcp.22450
Source: PubMed

ABSTRACT Induced pluripotent stem (iPS) cells can be generated from various embryonic and adult cell types upon expression of a set of few transcription factors, most commonly consisting of Oct4, Sox2, cMyc, and Klf4, following a strategy originally published by Takahashi and Yamanaka (Takahashi and Yamanaka, 2006, Cell 126: 663-676). Since iPS cells are molecularly and functionally similar to embryonic stem (ES) cells, they provide a source of patient-specific pluripotent cells for regenerative medicine and disease modeling, and therefore have generated enormous scientific and public interest. The generation of iPS cells also presents a powerful tool for dissecting mechanisms that stabilize the differentiated state and are required for the establishment of pluripotency. In this review, we discuss our current view of the molecular mechanisms underlying transcription factor-mediated reprogramming to induced pluripotency.

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Available from: Constantinos Chronis, Jul 12, 2015
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    • "Thanks to the recent research accomplishments in cellular reprogramming, previous studies have shown that cells are highly plastic [Hanna et al., 2011]. This plasticity is subject to the influence of critical transcription factors whose enforced expression can directly cause phenotypic changes in cells, including differentiation [Lavon et al., 2006; Liew et al., 2008], trans‐differentiation [Ho et al., 2011; Huang et al., 2011; Murry and Pu, 2011; Sekiya and Suzuki, 2011], and de‐differentiation [Hanna et al., 2008]. Therefore, it can be speculated that there are certain specific transcription factors, or a combination of transcription factors, that can facilitate the differentiation of ESCs, or even direct reprogram ESCs, into hepatocyte‐like cells. "
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    ABSTRACT: Hepatocytes can be generated from embryonic stem cells (ESCs) using inducers such as chemical compounds and cytokines, but issues related to low differentiation efficiencies remain to be resolved. Recent work has shown that overexpression of lineage-specific transcription factors can directly cause cells phenotypic changes, including differentiation, trans-differentiation, and de-differentiation. We hypothesized that lentivirus-mediated constitutive expression of forkhead box A2 (Foxa2) and hepatocyte nuclear factor 4 alpha (Hnf4a) could promote inducing mouse ESCs to hepatocyte-likes cells. First, ESC lines that stably expressed Foxa2, Hnf4a or Foxa2/Hnf4a were constructed via lentiviral expression vectors. Second, observations of cell morphology changes were made during the cell culture process, followed by experiments examining teratoma formation. Then, the effects of constitutive expression of Foxa2 and Hnf4a on hepatic differentiation and maturation were determined by measuring the marker gene expression levels of Albumin, α-fetoprotein, Cytokeratin18, and α1-antitrypsin. The results indicate that constitutive expression of Foxa2 and Hnf4a does not affect ESCs culture, teratoma formation, or the expression levels of the specific hepatocyte genes under autonomous differentiation. However, with some assistance from inducing factors, Foxa2 significantly increased the hepatic differentiation of ESCs, whereas the expression of Hnf4a alone or Foxa2/Hnf4a could not. Differentiated CCE-Foxa2 cells were more superior in expressing several liver-specific markers and protein, storing glycogen than differentiated CCE cells. Therefore, our method employing the transduction of Foxa2 would be a valuable tool for the efficient generation of functional hepatocytes derived from ESCs. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
    Journal of Cellular Biochemistry 11/2013; 114(11). DOI:10.1002/jcb.24604 · 3.37 Impact Factor
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    • "Using murine and deer cells should not cause problems considering the recent literature. Ho et al. (2011) realised that the diversity of cell types and species that have been reprogrammed and the general applicability of the four original reprogramming factors (Oct4, Sox2, c-Myc and Klf4) suggests a generic fashion in which the four factors act [49]. The authors concluded that there probably is no cell type-specific barrier that cannot be overcome by the action of the reprogramming factors leading to an evolutionary conserved pluripotency network. "
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    ABSTRACT: The octamer-binding transcription factor 4 (Oct4) was originally described as a marker of embryonic stem cells. Recently, the role of Oct4 as a key regulator in pluripotency was shown by its ability to reprogram somatic cells in vitro, either alone or in concert with other factors. While artificial induction of pluripotency using transcription factors is possible in mammalian cell culture, it remains unknown whether a potential natural transfer mechanism might be of functional relevance in vivo. The stem cell based regeneration of deer antlers is a unique model for rapid and complete tissue regeneration in mammals and therefore most suitable to study such mechanisms. Here, the transfer of pluripotency factors from resident stem cell niche cells to differentiated cells could recruit more stem cells and start rapid tissue regeneration. We report on the ability of STRO-1(+) deer antlerogenic mesenchymal stem cells (DaMSCs) to transport Oct4 via direct cell-to-cell connections. Upon cultivation in stem cell expansion medium, we observed nuclear Oct4 expression in nearly all cells. A number of these cells exhibit Oct4 expression not only in the nucleus, but also with perinuclear localisation and within far-ranging intercellular connections. Furthermore, many cells showed intercellular connections containing both F-actin and α-tubulin and through which transport could be observed. To proof that intercellular Oct4-transfer has functional consequences in recipient cells we used a co-culture approach with STRO-1(+) DaMSCs and a murine embryonic fibroblast indicator cell line (Oct4-GFP MEF). In this cell line a reporter gene (GFP) under the control of an Oct4 responsive element is only expressed in the presence of Oct4. GFP expression in Oct4-GFP cells started after 24 hours of co-culture providing evidence of Oct4 transfer from STRO-1(+) DaMSCs to Oct4-GFP MEF target cells. Our findings indicate a possible mechanism for the expansion of a resident stem cell niche by induction of pluripotency in surrounding non-niche cells via transfer of transcription factors through intercellular connections. This provides a new approach to explain the rapid annual antler regrowth.
    PLoS ONE 02/2012; 7(2):e32287. DOI:10.1371/journal.pone.0032287 · 3.53 Impact Factor
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    • "transcription factors. Yamanaka and collaborators successfully achieved the reprogramming of adult fibroblasts bypassing nuclear transfer and fusion approaches to obtain iPS [3] [4] [5]. First generation of mouse and human iPS were made by the incorporation of 4 transcription factors, Oct4, Sox2, c- Myc and Klf4 (known as Yamanaka factors) [4] [5]. "
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    ABSTRACT: A lot of effort has been developed to bypass the use of embryonic stem cells (ES) in human therapies, because of several concerns and ethical issues. Some unsolved problems of using stem cells for human therapies, excluding the human embryonic origin, are: how to regulate cell plasticity and proliferation, immunological compatibility, potential adverse side-effects when stem cells are systemically administrated, and the in vivo signals to rule out a specific cell fate after transplantation. Currently, it is known that almost all tissues of an adult organism have somatic stem cells (SSC). Whereas ES are primary involved in the genesis of new tissues and organs, SSC are involved in regeneration processes, immuno-regulatory and homeostasis mechanisms. Although the differentiating potential of ES is higher than SSC, several studies suggest that some types of SSC, such as mesenchymal stem cells (MSC), can be induced epigenetically to differentiate into tissue-specific cells of different lineages. This unexpected pluripotency and the variety of sources that they come from, can make MSC-like cells suitable for the treatment of diverse pathologies and injuries. New hopes for cell therapy came from somatic/mature cells and the discovery that could be reprogrammed to a pluripotent stage similar to ES, thus generating induced pluripotent stem cells (iPS). For this, it is necessary to overexpress four main reprogramming factors, Sox2, Oct4, Klf4 and c-Myc. The aim of this review is to analyze the potential and requirements of cellular based tools in human therapy strategies, focusing on the advantage of using MSC over iPS.
    Current Stem Cell Research & Therapy 02/2012; 7(3):191-6. DOI:10.2174/157488812799859865 · 2.86 Impact Factor
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