Proteomics analysis of human dentin reveals distinct protein expression profiles

The human tooth is the hardest organ of the body, and is composed of enamel, dentin, and dental pulp. Dentin provides the basis of the tooth shape by lining the inner parts of the root and crown. Odontoblasts deposit dentin, an organic matrix that contains collagen, noncollagenous proteins, phospholipids, and growth factors. In this study, we sought to reveal the proteins in human dentin by using liquid chromatography-tandem mass spectroscopy (LC-MS/MS) proteomic approaches. Human third molar dentins were cut, isolated, and demineralized, and the extracted proteins were separated on SDS-PAGE. In-gel digested peptides were analyzed using reverse-phase LC-MS/MS. We identified 233 total and 68 common proteins from 3 individuals with high confidence, including a variety of collagenous and noncollagenous proteins such as DSPP, biglycan, osteoglycin, osteopontin, and osteocalcin. In addition to known proteins, we also identified various matrix and serum proteins deposited in the dentin, including asporin, lumican, mimecan, and SOD3. This study provides the first list of proteomes that are detected in human dentin. This proteome list is useful in that it defines the organic matrix of dentin and helps to characterize odontoblasts.