No abstract

Proteomic analysis of the human body is a significant recent scientific endeavour. In this study, we investigated the proteomic profile of human dentin using modern analytical and mass spectrometric techniques. Five healthy permanent human molars from five adults were cut, pulverized, denaturated with guanidine buffer, and demineralized with EDTA buffer. The extracted proteins were analysed by gel electrophoresis (SDS-PAGE and two-dimensional gel electrophoresis), digested with trypsin, and separated by liquid chromatography/high-resolution tandem mass spectrometry. We identified 289 proteins with high confidence, 90 of which had not been previously detected in human dentin. Nine (currently hypothetical) proteins were identified for the first time in an actual human sample. The proteins have a variety of functions, including calcium-ion binding, formation of the extracellular matrix, formation of the cytoskeleton, cytoskeletal protein binding, immune response, and transport. In conclusion, this is the first use of two-dimensional electrophoresis for investigating human dentin.

The dentin–enamel junction (DEJ) is the border where two different mineralized structures – enamel and dentin – meet. The protein‐rich DEJ, together with the inner enamel region of mature teeth, is known to exhibit higher fracture toughness and crack growth resistance than bulk phase enamel. However, an explanation for this behavior has been hampered by the lack of compositional information for the DEJ and the adjacent enamel organic matrix (EOM). We studied proteomes of the DEJ and EOM of healthy human molars and compared them with dentin and enamel proteomes from the same teeth. These tissues were cut out of tooth sections by laser capture microdissection, proteins were extracted and cleaved by trypsin, then processed by liquid chromatography coupled to tandem mass spectrometry to analyze the proteome profiles of these tissues. This study identified 46 proteins in DEJ and EOM. The proteins identified have a variety of functions, including calcium ion‐binding, formation of extracellular matrix, formation of cytoskeleton, cytoskeletal protein binding, cell adhesion, and transport. Collagens were identified as the most dominant proteins. Tissue‐specific proteins, such as ameloblastin and amelogenin, were also detected. Our findings reveal new insight into proteomics of DEJ and EOM, highly mineralized tissues that are obviously difficult to analyze.