Awa et al., 2011; Laud et al., 2005; Multani and Chang, 2007). Telomere length in pluripotent WS cells appears to be standard. With differentiation premature senescence recurs, and aberrant telomere synthesis is found in derived MSCs, but not in NPCs, indicative of a lineage-specific aging phenomenon. This R916562 Autophagy observation is constant with all the clinical phenotype of WS, where mesenchymal tissues are severely affected but mild or no symptoms are connected with neural lineages (Goto et al., 2013). The inability to perform systematic research of different cell varieties or tissues through embryonic development and in adulthood validates iPSC technologies as a valuable tool to study its pathogenesis. By comparing the different stem/progenitor cells, we identified a dramatic difference in CYP2A6 Inhibitors products telomerase activity. In line with other studies,(D) Expression of p53 and senescence markers p21 and p16 proteins by Western blot analysis. WS MSCs express much more proteins of p53, p21, and p16. (E) Accelerated telomere attrition at late passage (p17) of WS MSCs as revealed by TRF Southern blot. (F) BrdU incorporation in between regular and WS MSCs. The difference is substantially distinctive (p 0.05). (G) Elevated incidence of defective synthesis for the lagging strand telomeres by CO-FISH. Arrows indicate the missing telomeres at metaphase. (H) Quantification of (F). Values represent mean SEM (at the very least 15 metaphase cells had been analyzed). Scale bar, 100 mm (C) or ten mm (G). See also Figure S3.Stem Cell Reports j Vol. two j 53446 j April eight, 2014 j 014 The AuthorsStem Cell ReportsTelomerase Protects against Lineage-Specific AgingFigure 4. Rescue of Premature Senescence in WS MSCs by Overexpression of hTERT or Knockdown of p53 (A and B) Elevated cell proliferation and replicative prospective in WS MSCs by overexpression of hTERT (A) or by p53 knockdown (p53i) (B). (C) The percentage of SA-b-galactosidasepositive cells is lowered by hTERT overexpression or by p53i. Values represent imply of technical replicates SD (n = 3). (D) Representative images of SA-b-galactosidase staining. (E) WS MSCs expressing hTERT show elongated telomere length compared to unmodified MSC. Telomere length is slightly shortened or unchanged in p53i MSCs. (F) CO-FISH analysis for the lagging strand telomeres in hTERT-expressing and p53i WS MSCs. Arrows indicate the missing telomeres from the lagging strand. (G) Quantification of (F). Values represent imply SEM (at least 15 metaphase cells were analyzed). Scale bar, one hundred mm (D) or 10 mm (F). See also Figure S4.telomerase activity is high in embryonic cells, and its activity declines with differentiation (Armstrong et al., 2000; Yang et al., 2008). MSCs and fibroblasts express low telomerase activity, which explains the vulnerability of these cells to replication-induced senescence and telomere dysfunction. The present study supports the critical role for telomerase in preventing certain lineages of cells from accelerated aging, and it may have an effect on stem cell renewal and their capacity for regeneration (Blasco, 2007). Our observation is constant using the Wrn knockout mouse model, which does not recapitulate the pathogenesis in the disease unless it is expressed on a background of Terc(Chang et al., 2004; Lombard et al., 2000). How telome-rase rescues telomere dysfunction isn’t clear; even so, telomerase was reported to extend telomeres and rescue premature aging and reverse tissue degeneration in aged Tercmice with shortened telomeres (Jaskelioff et al., 2011; Sa.