Background: In mammals, tooth crown formation completes before eruption, but enamel can harden or decay after eruption with saliva playing a critical role in these processes. However, the role of salivary proteases and peptides in post-eruptive enamel hardening is unresolved. The mechanism of enamel formation is highly conserved in mammals, although speed and eruption timing vary between species. Compared to humans, pig teeth form very fast and erupt with less mineralized enamel that hardens further after eruption to withstand chewing forces. Our working hypothesis is that post-eruptive porcine enamel mineralization is mediated by saliva proteases and pellicle components that facilitate removal of enamel matrix proteins and influx of mineral ions to grow enamel crystals. The goal of this work is to characterize the protein composition of porcine whole saliva, plaque/pellicle and enamel at different stages after eruption. The purpose of this work is to resolve and leverage the mechanism of this rapid and marked enamel hardening to avoid dental decay in pigs and use the pig model for human dental research.
Methods: Saliva samples were collected from pigs 2, 4 and 16 weeks old using ropes, pigs sacrificed, and dentitions collected. Trypsin digestion and analysis by LC-MS/MS were performed after protein extraction. PEAKS software was used to identify protein composition and compare protein abundances.
Findings: Preliminary saliva data from 2-, 4- and 16-week-old pigs (n=1 pig per age) showed differences in protein profiles and abundances. Mmp9 and Klk peptides were identified with proteases, e.g. Cathepsin D, Alpha-1-antitrypsin, Serpin, Lipocalin (a binding protein), Serum albumin and IgG.
Conclusions: The developmental differences of pigs are also observed in proteomic profiles in saliva. Analyses of additional saliva and enamel samples are ongoing to validate these results and test their participation in enamel mineralization processes.