A short-term treatment with tumor necrosis factor-alpha (TNF-α) enhances the stem cell phenotype of dental pulp stems (DPCs). (A) Immunofluorescence analysis of expression of stem cell markers STRO-1, CD146, and stage-specific embryonic antigen 4 (SSEA-4) upon TNF-α treatment. Treatment with TNF-α markedly increased the number of cells positive for the three markers. (B) Flow cytometric analysis of expression of SSEA-4 and CD146. TNF-α treatment increased by twofold the number of cells positive for SSEA-4. Odontogenic differentiation decreased the percentage of SSEA-4+ and CD146+ cells, demonstrating that expression of these markers is closely related to their differentiation stage. (C) Effects of TNF-α pretreatment on mRNA levels of stem cell markers OCT-4 and NANOG. TNF-α treatment significantly increased the gene expression of OCT-4 and NANOG. (D) Analysis of telomerase activity between TNF-α-treated and untreated DPCs. TNF-α treatment significantly increased telomerase activity of DPCs. *P <0.05, **P <0.01, unpaired t test. Images and graphs are representative of at least three different experiments.