Functional analysis of protein S100A7 in pulpal wound healing process

Objectives: Organic dentin matrix components (DMCs) contain various kinds of bioactive molecules, which can be released by enzymatic digestion of DMCs during caries progress. We previously identified specific molecules from digested DMCs induced by MMP-20 promoted wound healing process of pulp. Protein S100A7 found in the digested DMCs is one of the most effective molecules to induce tertiary dentinogenesis, but the functional domain or target molecules of this protein is still unclear. In this study, functional analysis was performed to investigate the mechanism of promoting tertiary dentin formation by S100A7.
Methods: Direct pulp capping experiment was performed using S100A7 treated with MMP-20 or no-treated S100A7 in Wistar rat molars. The pulp capped teeth were collected 4week after operation and evaluated by micro-CT and histological analysis. Animal studies were conducted under the approval of the Institutional Animal Care and Use Committee of Osaka University Graduate School of Dentistry (No.28-014-0). Sequence alignment at different mammalian species of S100A7 was compared to identify functional domains using UniProt (data bank of protein) and CLUSTALW (program for preparing sequence alignment).Pull down assay was performed to search for the target molecules of S100A7 in dental pulp tissue using rat primary pulp cells and recombinant human S100A7, then the results were confirmed by SDS-PAGE.
Results: Both MMP-20 treated S100A7 and no-treated S100A7 promoted tertiary dentin formation in vivo. S100A7 showed high homology among five mammalians at metal binding site of protein structure in silico. Pull down assay showed several specific proteins were interacted with S100A7.
Conclusions: Protein S100A7 promoted tertiary dentin formation with or without treatment by MMP-20. Metal binding site of S100A7 can be related to the promotion of tertiary dentin formation. Some specific candidate molecules that might interact with S100A7 in the pulp tissue could facilitate tertiary dentinogenesis.
This study was supported by JSPS KAKENHI (17K11704, 17H06848,17H04382)