Awa et al., 2011; Laud et al., 2005; Multani and Chang, 2007). Telomere length in pluripotent WS cells appears to be normal. With differentiation premature senescence recurs, and aberrant telomere synthesis is identified in derived MSCs, but not in NPCs, indicative of a lineage-specific aging phenomenon. This observation is constant using the clinical phenotype of WS, where mesenchymal tissues are severely affected but mild or no symptoms are associated with neural lineages (Goto et al., 2013). The inability to 4-Epianhydrotetracycline (hydrochloride) Bacterial perform systematic studies of diverse cell kinds or tissues during embryonic improvement and in adulthood validates iPSC technologies as a useful tool to study its pathogenesis. By comparing the diverse stem/progenitor cells, we identified a dramatic distinction in telomerase activity. In line with other studies,(D) Expression of p53 and senescence markers p21 and p16 proteins by Western blot evaluation. WS MSCs express a lot 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 involving normal and WS MSCs. The difference is significantly different (p 0.05). (G) Increased 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 (a minimum of 15 metaphase cells have 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 four. Rescue of Premature Senescence in WS MSCs by Gene Inhibitors MedChemExpress overexpression of hTERT or Knockdown of p53 (A and B) Elevated cell proliferation and replicative potential 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 = three). (D) Representative pictures of SA-b-galactosidase staining. (E) WS MSCs expressing hTERT show elongated telomere length when compared with unmodified MSC. Telomere length is slightly shortened or unchanged in p53i MSCs. (F) CO-FISH evaluation for the lagging strand telomeres in hTERT-expressing and p53i WS MSCs. Arrows indicate the missing telomeres in the lagging strand. (G) Quantification of (F). Values represent mean SEM (at the least 15 metaphase cells have been analyzed). Scale bar, 100 mm (D) or ten mm (F). See also Figure S4.telomerase activity is higher 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 vital function for telomerase in stopping particular lineages of cells from accelerated aging, and it may affect 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 really is expressed on a background of Terc(Chang et al., 2004; Lombard et al., 2000). How telome-rase rescues telomere dysfunction isn’t clear; on the other hand, 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.