Abstract 12940: Insulin Growth Factor-1 Enhances Telomerase Activity and Prevents Mitochondrial Dysfunction via the p53/PGC Network in Human Induced Pluripotent Stem Cells
Background. Reprogramming somatic cells into induced pluropotent stem cells (iPS) using transcription factors offers a novel approach for regenerative medicine. However, the potential for clinical application of iPS has several obstacles, including early senescence during passage. A reduced telomerase activity in association with mitochondrial dysfunction via the p53/ PPARγ coactivator pathway (PGC) contributes to cardiovascular senescence. This study tested the hypothesis that insulin-like growth factor (IGF-1) and its downstream PI3K/AKT signaling prevented iPS mitochondrial dysfunction via the telomerase/p53/PGC pathway.
Methods and Results. Human dermal fibroblasts were transduced with reprogramming factors (Oct4, Sox2, Klf4 and c-myc) using a lentiviral vectors. Quantitative real-time PCR and stem cell protein array showed that IGF-1 treatment significantly increased mRNA and protein levels of Oct4 and Nanog in the transduced cells. Moreover, the telomerase activity was increased by IGF-1 (IGF-1 vs. control = 14.3 ± 0.5 vs 5.6 ± 0.4 arbitrary units, p<0.05) as assessed using the TRAPeze Telomerase Detection Assay. IGF-1 also decreased p53 mRNA (3.2 ± 0.4 fold, p<0.01) and p53 protein (2.5 ± 0.4 fold, p<0.05). By contrast, IGF-1 increased mRNA expression of PGCs, which were targets of p53 and master mitochondrial regulators. IGF-1 also increased mitochondrial biogenesis (indicated by mtDNA copy number, e.g., complex I and complex V mRNA expression), mitochondrial mass (assessed by Mitotracker Red and Mitotracker Green) and energy production (ATP level). In addition, the above effects of IGF-1 could be attenuated by IGF-1 receptor neutralizing antibodies and PI3 kinase inhibitor LY294002, but not by mitogen-activated protein/ERK kinase inhibitor PD98059.
Conclusion. IGF-1 enhances telomerase activities and prevents mitochondrial dysfunction during iPS passage. The effects of IGF-1 may be mediated by the PI3 kinase pathway. IGF-1 may serve as a potential regulatory factor for iPS development and senescence. Its role in the telomerase/p53/PGC/mitochondria network shed new insight into the therapeutic options by employing IGF-1 treated iPS cells for repair of injured cardiovascular tissues.
- © 2011 by American Heart Association, Inc.