Dental pulp stem cell (DPSC) growth on fluorapatite (FA) surfaces

Recently, we reported the synthesis of an organized nano FA prism-like structure that has similar composition and topography to enamel (Chen et al., 2006b). Eventually using these nano FA surfaces and DPSC cells we would like to create a functional enamel/dentin junction. Objectives: In this study, the DPSC cells are grown on organized and disorganized FA surfaces to study the initial cellular response and the underlying mechanisms during this process. Methods: The cells were subcultured in 10% FBS DMEM for 7 days on the two surfaces. Specimens were observed under SEM, counted, and analyzed using the human pathway-focused matrix and adhesion PCR array. Results: The cells had a three-dimensional morphology and the two surfaces showed excellent biocompatibility. After 7 days, the cell number on organized FA surface was significantly higher than on the disorganized surface. Of the 84 focused pathway genes, a total of 20 genes were either up or down regulated in the cells on organized FA surface compared to the disorganized surface. Of the cell-matrix adhesion molecules, secreted phosphoprotein 1 (SPP1), thrombospondin 3 (THBS3), integrin alpha 7 and 8 (ITGA 7 and 8), integrin beta 3 and 4 (ITGB3 and 4), and more interestingly, the vitronectin receptor-integrin alpha V (ITGAV) were up-regulated. Other adhesion molecules for example collagen type VII alpha 1 (COL7A1), COL8A1, COL12A1, laminin alpha1 (LAMA1) and the key adhesion protein-fibronectin1 (FN1) were also up-regulated. Among the ECM proteases, the up-regulation of the matrix metalloproteinase 13 (MMP13) was coordinated with the down-regulation of 3 other proteases. Conclusion: The enhanced cellular response of DPSC cell to the organized FA crystal surface involves a set of delicately regulated matrix and adhesion molecules. The DPSC cells will in the future be treated with a dentin extract to create a dentin/enamel junction. This study was supported by NIH grants DE015599.