Se with the stabilization of p53 by telomeric repeats (Milyavsky et al., 2001). Nonetheless, activation of p53 was not improved in WS-MSCtert despite the higher basal level (Figure S4I). An additional senescence marker p16, as expected, was decreased in WS-MSCtert. When WS MSCs were exposed to H2O2, 53BP1 was activated at low oxidative strain (50 mM), whereas gH2AX was induced at high oxidative tension (250 mM) accompanied by activation of ATM (p-ATM) (Figure S4E). The expression of hTERT in WS MSCs seems to rescue senescence through reduction of the p16 level (but not of p53/p21) and also the DNA damage marker gH2AX. These data support the vital role of telomerase in cell proliferation along with the cell’s replicativepotential, too as in preventing DNA damage and premature senescence in WRN-deficient cells. We recommend that, with out protection of the telomere by telomerase, WS cells swiftly enter senescence through the p53 pathway. To verify this postulation, we derived stable p53 knockdown cells by RNAi (p53i) in WS fibroblasts. When these p53i WS cells were reprogrammed to iPSCs, they showed little distinction from unmodified iPSCs; on the other hand genomic instability was present (Table S2). Genomic instability as a consequence of p53 depletion in iPSCs has been previously reported (Kawamura et al., 2009; Marion et al., 2009a). Upon differentiation to MSCs (WS-MSCp53i), p53 protein remains low, proof of persistent expression of p53 shRNA (Figure S4F). As a consequence in MSCs, p53i enhanced their proliferative prospective and rescued the premature senescence phenotype without having the have to have for high telomerase activity and lengthy telomere length (Figures 4BD). As expected, WS-MSCp53i expressed less p21 and phosphorylated p53 (Figure S4G). Next, we examined the telomere status in these genetically modified cells. Longer telomere length was discovered in WS-MSCtert, but not in WS-MSCp53i, suggesting a rescue in the accelerated telomere attrition by telomerase (Figure 4E). Fucosyltransferase Inhibitors products CO-FISH evaluation revealed a reduction of defective Bifeprunox Biological Activity synthesis for the lagging strand telomeres in WS-MSCtert, but not in WS-MSCp53i (Figures 4F and 4G). Collectively, these information help the important part of telomerase in preventing premature senescence in MSCs by restoring telomere function. p53 appears to be a downstream effector mainly because a related impact was achieved as a consequence of depleting p53 and bypassing the senescence pathway.Stem Cell Reports j Vol. 2 j 53446 j April eight, 2014 j 014 The AuthorsStem Cell ReportsTelomerase Protects against Lineage-Specific AgingFigure three. Recurrence of Premature Senescence and Telomere Dysfunction in WS MSCs (A) Decreased cell proliferation and replication prospective in WS MSCs with continuous culture for 76 days. (B) Quantitative analysis for percentage of senescent cells in MSCs following 44 days of culture (p11). A significant distinction is identified among typical and WS MSCs (p 0.05).Values represent imply of technical replicates SD (n = 3). (C) Representative images for regular and WS MSCs by SA-b-galactosidase staining. (legend continued on subsequent page)538 Stem Cell Reports j Vol. 2 j 53446 j April 8, 2014 j 014 The AuthorsStem Cell ReportsTelomerase Protects against Lineage-Specific AgingTelomerase Activity in NPCs and Its Function in Defending DNA Damage For the reason that telomerase features a critical function in protection of telomere erosion in MSCs, we speculate that the neural lineage telomerase is differentially regulated and protects neural lineage cells from accelerated senescence. To test.