Effects of predentin and dentine proteins on collagen fibrillogenesis

Objectives: To investigate the proteome of the extracellular matrix in the transition from predentine to dentine and to determine which proteins are involved in dentinogenesis. Methods: Proteins were extracted from bovine teeth as described previously (Waddinton RJ, Hall RC, Embery G, Lloyd DM 2003 Calcif Tissue Int 56: 236-9. Predentine and dentin were divided into fractions by weight using FPLC. Fibrillogenesis was determined from the change in absorbance, measured over 3 hours at 405nm, of a 0.8 mg/ml collagen solution at 25oC. Results: The endpoint of the fibrillogenesis assay was significantly (P<5%) depressed by dentine matrix proteins at concentrations greater than 0.14 mg/ml and by predentine matrix proteins (P<1%) at concentrations greater than 0.04mg/ml. Low concentrations (<0.004mg/ml) of dentine, but not predentine, significantly (P<5%) enhanced the endpoint of the assay and also increased the half time of the rate of fibrillogenesis from 24 to 39 minutes. FPLC fractionation of dentine samples indicate that depression of the endpoint of the fibrillonenesis assay was produced by proteins contained in more than one fraction. Conclusion: Proteins extracted from predentin and dentine consistently alter the rate and extent of fibrillogenesis. Profiling the proteome of each phase of dentinogenesis will allow us to determine which proteins are involved in the regulation of biomineralisation.