Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by defined factors. However, the low efficiency and slow kinetics of the reprogramming process have hampered progress with this technology. Here we report that a natural compound, vitamin C (Vc), enhances iPSC generation from both mouse and human somatic cells. Vc acts at least in part by alleviating cell senescence, a recently identified roadblock for reprogramming.
In addition, Vc accelerates gene expression changes and promotes the transition of pre-iPSC colonies to a fully reprogrammed state. Our results therefore highlight a straightforward method for improving the speed and efficiency of iPSC generation and provide additional insights into the mechanistic basis of the reprogramming process.► Vitamin C improves the speed and efficiency of mouse iPSC generation ► Adding vitamin C converts pre-iPSCs to iPSCs ► Vitamin C alleviates the senescence roadblock to reprogramming ► Human iPSC generation is also improved by vitamin C
Animal development starts with the fertilized egg undergoing a programmed process of cell proliferation and differentiation that generates all cell types of an individual. This process was thought to be irreversible in mammals, but the cloning of Dolly proved that fully differentiated somatic cell nuclei can be reprogrammed back to an embryonic-like state by factors present in oocytes (Wilmut et al., 1997). More recently, Yamanaka and colleagues demonstrated that mouse somatic cells can also acquire a pluripotent state in vitro after the introduction of a defined combination of transcription factors that are highly enriched in embryonic stem cells (ESCs) (Takahashi and Yamanaka, 2006). Mouse iPSCs are similar to ESCs in most aspects and can generate entire individuals after tetraploid complementation (Kang et al., 2009,Okita et al., 2007,Wernig et al., 2007,Zhao et al., 2009).
iPSCs have also been produced from other species including human and pig (Esteban et al., 2009,Takahashi et al., 2007,Yu et al., 2007), raising the possibility of clinical application of personalized stem cell-based therapies without immune rejection or ethical concerns. Human iPSCs also provide a unique platform for studying genetic diseases in vitro (Park et al., 2008).
However, the low efficiency of iPSC generation is a significant handicap for mechanistic studies and high throughput screening, and also makes bona fide colony isolation time consuming and costly. The efficiency of alkaline phosphatase-positive (AP+) colony formation with the four Yamanaka’s factors (Sox2, Klf4, Oct4, c-Myc; SKOM) in mouse fibroblasts is about 1% of the starting population, but only around 1 in 10 of those colonies is sufficiently reprogrammed to be chimera competent (Silva et al., 2008). In human fibroblasts, only about 0.01% of cells transduced with SKOM form AP+ iPSC colonies (Takahashi et al., 2007,Yu et al., 2007).
In our search for compounds that improve the efficiency of somatic cell reprogramming, we have found that a vitamin (Vc) that is highly abundant in our diet significantly increases mouse and human iPSC colony formation, at least in part by alleviating cell senescence.
Results: Vitamin C Can Improve iPSC Generation
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