Signalling Mineralisation in Dental Pulp Derived Cells

Objectives: Signalling of mineralisation in the mature tooth is a key event associated with both peritubular dentinogenesis and regenerative processes after injury in the dentine-pulp complex. We investigate whether solubilised dentine matrix proteins can stimulate mineralisation in dental pulp derived cells. Methods: Dentine matrix proteins (DMPs) were isolated by extraction of dissected and powdered sound human dentine with 10% (w/v) EDTA, pH 7.2, containing protease inhibitors for 7 days at 4^oC followed by dialysis and lyophilisation. Odontoblast-like (MDPC-23) and pulp-derived (OD-21) cell lines, kindly provided by Dr J Nor (University of Michigan), and the 3T3 fibroblast-like cell line were cultured in DMEM medium with 10% FCS for 3, 7, 11, 14 and 18 days in the presence of various mineralisation supplements including a) β-glycerophosphate (βGP) and ascorbic acid (AA) [basal mineralisation supplement], b) βGP + AA + DMPs (1µg/ml) [experimental mineralisation supplement], c) βGP + AA + dexamethasone (DEX) [control mineralisation supplement]. Viable cell numbers were assessed by trypan blue staining and mineralisation was quantified by image analysis of von Kossa stained cultures. Mineralisation was expressed as % per cell by dividing the area of mineralisation by viable cell count. Results: Basal levels of mineralisation were observed in the MDPC-23 and OD-21 cells and to a much lesser extent within the 3T3 cell line in the cultures with basal mineralisation supplement. A significant increase in mineralisation was seen with both the addition of DMPs and the control mineralisation supplement. Conclusion: This work demonstrates that solubilised dentin matrix proteins can stimulate mineralization in dental pulp derived cells.