SummaryReprogramming of somatic cells to a pluripotent state was first accomplished using retroviral vectors for transient expression of pluripotency-associated transcription factors. This seminal work was followed by numerous studies reporting alternative (noninsertional) reprogramming methods and various conditions to improve the efficiency of reprogramming. These studies have contributed little to an understanding of global mechanisms underlying reprogramming efficiency. Here we report that inhibition of the mammalian target of rapamycin (mTOR) pathway by rapamycin or PP242 enhances the efficiency of reprogramming to induced pluripotent stem cells (iPSCs). Inhibition of the insulin ⁄ IGF-1 signaling pathway, which like mTOR is involved in control of longevity, also enhances reprogramming efficiency. In addition, the small molecules used to inhibit these pathways also significantly improved longevity in Drosophila melanogaster. We further tested the potential effects of six other longevity-promoting compounds on iPSC induction, including two sirtuin activators (resveratrol and fisetin), an autophagy inducer (spermidine), a PI3K (phosphoinositide 3-kinase) inhibitor (LY294002), an antioxidant (curcumin), and an activating adenosine monophosphate-activated protein kinase activator (metformin). With the exception of metformin, all of these chemicals promoted somatic cell reprogramming, though to different extents. Our results show that the controllers of somatic cell reprogramming and organismal lifespan share some common regulatory pathways, which suggests a new approach for studying aging and longevity based on the regulation of cellular reprogramming.

Objective-Endothelial progenitor cells (EPCs) contribute to postnatal neovascularization and are therefore of great interest for autologous cell therapies to treat ischemic vascular disease. However, the origin and functional properties of these EPCs are still in debate. Methods and Results-Here, ex vivo expanded murine EPCs were characterized in terms of phenotype, lineage potential, differentiation from bone marrow (BM) precursors, and their functional properties using endothelial NO synthase (eNOS)-green fluorescent protein transgenic mice. Despite high phenotypic overlap with macrophages and dendritic cells, EPCs displayed unique eNOS expression, endothelial lineage potential in colony assays, and angiogenic characteristics, but also immunologic properties such as interleukin-12p70 production and low levels of T-cell stimulation. The majority of EPCs developed from an immature, CD31 ϩ Ly6C ϩ myeloid progenitor fraction in the BM. Addition of myeloid growth factors such as macrophage-colony-stimulating factor (M-CSF) and granulocyte/ macrophage (GM)-CSF stimulated the expansion of spleen-derived EPCs but not BM-derived EPCs. Conclusion-The close relationship between EPCs and other myeloid lineages may add to the complexity of using them in cell therapy. Our mouse model could be a highly useful tool to characterize EPCs functionally and phenotypically, to explore the origin and optimize the isolation of EPC fractions for therapeutic neovascularization. [1][2][3] These cells have the potential to differentiate toward endothelial cells (ECs) and are therefore named endothelial progenitor cells (EPCs). Transplantation of EPCs has been shown to be effective in animal models for re-endothelialization 4,5 and adult neovascularization 6,7 as well as in human patient studies aimed to enhance myocardial regeneration after acute myocardial infarction. 7 Although EPCs are used in clinical trials, the exact phenotypic and lineage/ differentiation parameters of ex vivo-expanded EPCs are poorly defined, and it is not clear which cell populations will be most effective in repair studies. EPCs can be derived from CD34ϩ as well as CD34Ϫ or CD34 low cells and can be isolated and expanded ex vivo using BM aspirates and PB CD14ϩ mononuclear cell fractions. 8 -12 In many studies, EPCs are characterized by their adhesive spindle-like morphology, staining with the EC-binding lectin Ulex europaeus agglutinin (Ulex), and the capacity to endocytose acetylated low-density lipoprotein (acLDL). 2,11 Although this may generally suffice for EPC studies dealing with EPCs obtained from healthy animal models or humans, the different culture conditions and sources used may lead to a large heterogeneity and functionally suboptimal EPC populations. 13,14 It has even been suggested that transplantation of certain cell fractions may contribute to adverse side effects. 15 Clinical studies demonstrated that in patients experiencing diabetes and hypertension, the number of circulating EPCs is severely decreased, and the cells are dysfunctional. 16 -...

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