gene expression levels in long-term cultures of human dental pulp stem cells

In previous studies, human dental pulp stem cells (hDPSCs) were mainly isolated from adults. In this manuscript, we tried characterization of hDPSCs isolated from an earlier developmental stage to evaluate potential usage of these cells for tissue regenerative therapy. hDPSCs isolated at the crown-completed stage showed a higher proliferation rate than those isolated at the later stage. When the cells from either group were cultured in medium promoting differentiation towards cells of the osteo/odontoblastic lineage, both became alkaline phosphatase positive, produced calcified matrix, and were also capable of forming dentin-like matrix on scaffolds in vivo. However, during long-term passage, these cells underwent a change in morphology and lost their differentiation ability. The results of a DNA array experiment showed that the expression of a number of genes, such as WNT16, was markedly changed with increasing number of passages, which might have caused the loss of their characteristics as hDPSCs. Keywords: gene expression study, long-term cultures To identify genes modulated by passage, we performed cDNA microarray analysis on 3 independent samples at the crown-completed stage (DP2, 28, and 31) that had undergone P4 or P10. Human gene expression was examined by using a Human Genome U133 Plus 2.0 probe array (GeneChip; Affymetrix, Santa Clara, CA, USA), and a Hewlett-Packard Gene Array Scanner (Palo Alto, CA, USA). Each sample was analyzed once. The fluorescence intensity of each probe was quantified by GeneChip Analysis Suite 5.0 (Affymetrix). The level of gene expression was determined as the average difference, obtained by using the GeneChip software.