Comparative Proteomic Profiling of Enamel of Neonatal Teeth and Normal Primary Teeth Using Liquid Chromatography-Mass Spectrometry Approach.

Purpose: To identify the differentially expressed proteins in the enamel of neonatal teeth versus control enamel of primary teeth through a proteomics workflow. Methods: This study involved a total of 12 primary teeth (six neonatal teeth and six control primary teeth), from which enamel blocks were sectioned. These prepared blocks were then subjected to various processes involving acid etching, desalting, reduction, and alkylation of proteins, followed by overnight tryptic digestion, to prepare protein samples for bottom-up liquid chromatography tandem mass spectrometric (LC-MS/MS) analysis. Differential expression and functional annotation of proteins were carried out using specialized bioinformatics software. Results: Enamel samples of neonatal teeth displayed an increased abundance of proteins in comparison to the control enamel of primary teeth. Elevated expression of proteins involved in osteogenesis and mineralization processes was observed in neonatal teeth enamel. However, this was accompanied by a reduced expression of KLK-4 and downregulation of levels of the protease inhibitors, suggestive of an imbalance in the protease/protease inhibitor ratio. Further, the present data points toward increased expression of odontogenic ameloblast-associated protein (ODAM) as at least one of the causative factors for the early eruption of teeth. The enrichment of proteins involved in the complement and coagulation pathways also suggests the possibility of injury or pathogen infection. Conclusion: Neonatal teeth can serve as a natural model for the detailed analysis of the functions of elevated enamel proteins in their morphogenetic growth.