The Behavior of MDPC-23 Cells Modulated by DSPP

Abstract Phosphophoryn (PP) and Dentin Sialoprotein (DSP) are two of the most abundant dentin matrix non-collagenous proteins. These two proteins are derived from Dentin Sialophosphoprotein (DSPP) precursor protein cleavage by DMP1 protease. PP was well established as a nucleator to initiate dentin mineralization. The expression of DSPP precursor protein was reported to be required for normal odontoblast lineage differentiation. DSPP protein was also reported to modulate cell migration, cell proliferation and differentiation, leading to dentin formation. To further understand the role of DSPP in odontoblast lineage, we used MDPC23 cells to examine the mineralization process and the effects of DSPP on this process. MDPC23 cell line is an odontoblast-like cells, which exhibits unique features of dental pulp stem cells such as high alkaline phosphatase activity and expression of odontoblast markers: DSP and PP. MDPC23 cells were cultured in Mineralization Medium (MM) containing mineral inducing molecules (i.e., 100 µg//ml ascorbic acid, 10 mM β-glycerol phosphate and 10 nM dexamethasone) to examine MM effects on the cell growth and mineral deposition. Recombinant DSPP protein was used to test its effects on dental pulp cell growth and mineralization. We found that MDPC23 cells cultured with mineralization medium, proliferated slowly and spread widely at 4d. However, MDPC 23 cells in MM group, shrank and gradually detached from the well surface at 6d. Strong mineral deposition was detected with Alizarin Red staining at 7d. In the presence of recombinant DSPP protein (recDSPP), MDPC23 cells cultured with mineralization medium, also proliferated slowly, spread widely but remained vital from 4d, 6d, 7d, 8d, 9d, 10d, 12d through 18d and 20d. Strong mineral deposition was detected with Alizarin Red staining at 18d and 20d. Thus under the combined MM and recDSPP treatment, MDPC23 cells maintained the cell vitality and delayed the mineralization process. This study lent support that DSPP is required for maintaining normal odontoblast lineage. Keywords Cell maintenance; Dental pulp cells; Mineralization; Recombinant DSPP