The Enamel Protein Amelotin is an Inducer of Hydroxyapatite Mineralization in a Collagen Matrix

Objectives: The enamel protein Amelotin (AMTN) is predominantly expressed during the maturation stage of enamel development. It induces hydroxyapatite mineralization and is involved in the formation of the enamel surface layer. The objective of this study was to determine whether AMTN retains its mineral-inducing properties in a collagen-based matrix.
Methods: Recombinant human AMTN was expressed in bacteria and purified by affinity chromatography. The protein was adsorbed to commercially available collagen membranes and in-house produced collagen gels. In addition, warthog dentin slices were similarly conditioned with AMTN solution. Such treated collagen matrices were incubated in simulated body fluid (SBF) and the formation of mineral deposits analyzed by scanning electron microscopy. The nature of the mineral phase was determined by selected area electron diffraction (SAED) analysis.
Results: The application of AMTN to collagen membranes, gels and dentin surfaces induced the formation of hydroxyapatite mineral deposits in all cases, compared to non-treated controls.
Conclusions: Recombinant human AMTN protein, when adsorbed to collagen fibers or collagen-containing mineral matrices, induces the formation of hydroxyapatite mineral deposits and may be a useful approach biological therapy approach for conditions where formation of a hydroxyapatite interface is required. Examples include reattachment of Sharpey's fibers in the periodontium, pulp capping in endodontic treatment and tendon/ligament attachemnt in orthopaedic applications.