DMP-1 and DSPP in human sclerotic dentin: an immunohistochemical analysis

Objective:  To understand the mechanisms underlying dentin repair, several studies focused on the analysis of the morphological aspects and chemical content of human carious dentin. Demineralization of dentin matrix causes a series of defensive reactions of the dentin-pulp complex to the carious stimuli, resulting in the formation of intratubular hypermineralized dentin (sclerotic dentin) towards the advancing front of the carious lesion and in the apposition of tertiary dentin within the pulp chamber.

The objective of this study was to investigate the immunohistochemical labeling patterns of dentin matrix protein-1 (DMP-1) and dentin sialophosphoprotein (DSPP) in human sclerotic vs sound dentin matrix. 

Methods:  Sclerotic and sound human teeth were fixed in 4% paraformaldehyde and then processed for embedding in a methylmethacrylate-based resin system. Sections were exposed to a post-embedding immunolabeling procedure with anti-DMP-1 and anti-DSPP antibodies. An HRP-DAB-based detection system and gold-conjugated secondary antibodies were used to identify the antigen-antibody binding sites by means of light microscope and electron transmission microscope (TEM) respectively.

Results:  Sclerotic and sound dentin showed a positive immunoreactivity to both DMP-1 and DSPP antibodies. In particular DMP-1 and DSPP patterns were more intense in sclerotic than in sound dentin. The detection of DSPP was higher in the predentin layer, while labeling of DMP-1 was more concentrated in the dentin layer closer to predentin.

Conclusions:  These results suggest that both DSPP and DMP-1 may play an important role in the response of dentin to carious stimuli. In particular, these proteins might be involved in the hypermineralization of the sclerotic dentin portion of the human dentin matrix.