Increased matrix metalloproteinase-2 and bone sialoprotein response to human coronal caries

Abstract

Background: It has been suggested that host matrix metalloproteinase-2 (MMP-2) present in dentin may be involved in caries progression, however, its response to caries is not known. Bone sialoprotein (BSP) has been implicated in dentin mineralization and MMP-2 modulation.

Objective: To identify and compare the distribution of MMP-2 and BSP in healthy human coronal dentin and those with early caries.

Methods: Freshly extracted 3rd molars and premolars with and without early caries were fixed, demineralized and subjected to immunohistochemistry using a monoclonal anti-MMP-2 antibody and monoclonal anti-BSP antibody with an avidin-biotin complex method. Immunoreactivity was visualized with 3,3'-diaminobenzidine substrate and observed under light microscopy.

Results: Immunohistochemical analysis revealed that MMP-2 and BSP are not detected in the tubule lumens of healthy dentin. However, intense immunoreactivity for MMP-2 and BSP was detected in association with the full length of the caries-affected dentinal tubules. The MMP-2 and BSP at the dentino-enamel junction appeared unaltered.

Conclusion: The results indicate that MMP-2 and BSP may be actively secreted by odontoblasts in response to carious insult. MMP-2 and BSP accumulation in the caries-affected dentinal tubules may indicate their potential involvement in the host defense mechanism which results in calcification of regions affected by the carious process.

Fig. 1.

Western blot analysis using Ab-3 (anti-MMP-2) to detect rhMMP-2. Lane 1 = rhMMP-2 (∼61 kDa); lane 2 = apparent MW standards.

Fig. 2.

Western blot analysis using LFMb-25 (anti-BSP) to detect rhBSP. Lane 1 = rhBSP (∼75–90 kDa); lane 2 = apparent MW standards.

Fig. 3.

Immunodetection of MMP-2 in demineralized sections of sound coronal dentin. Increased immunoreactivity of MMP-2 was observed in association with the odontoblastic processes and mantle dentin (adjacent to the DEJ). No MMP-2 was detected in the dentinal tubules. Approximate region of higher magnification indicated by outline on the image above. Sections were counterstained with hematoxylin.

Fig. 4.

Immunodetection of BSP in demineralized sections of healthy coronal dentin. Increased immunoreactivity of BSP was observed in association with the odontoblastic processes. No BSP was detected in the dentinal tubules. A slight increase in BSP immunoreactivity was identified in the mantle dentin immediately adjacent to the DEJ. Sections were counterstained with hematoxylin.

Fig. 5.

a Image of mineralized section revealing caries and changes in mineralized dentin (arrows). b Image of anatomically oriented, demineralized section of the same tooth that had been probed for MMP-2. Intense immunoreactivity for MMP-2 was identified in association with the dentinal tubules in the area of caries-affected dentin.

Fig. 6.

Image of carious tooth section probed with anti-MMP-2 antibody revealing an intact DEJ and staining within the caries-associated dentinal tubules. Region of higher magnification indicated by outline on the right image.

Fig. 7.

Image of carious tooth section probed with anti-MMP-2 antibody revealing generalized typical staining of odontoblastic processes in the inner 200 μm of the dentin and staining within the caries-associated dentinal tubules. Region of higher magnification indicated by outline on the right image.

Fig. 8.

a Image of mineralized section revealing caries and changes in mineralized dentin (arrows). b Image of anatomically oriented, demineralized section of the same tooth that had been probed for BSP. Intense immunoreactivity for BSP was identified in association with the dentinal tubules in the area of caries-affected dentin.

Fig. 9.

Image of carious tooth section probed with anti-BSP antibody revealing an intact DEJ and staining within the caries-associated dentinal tubules. Region of higher magnification indicated by outline on the right image.

Fig. 10.

Image of carious tooth section probed with anti-BSP antibody revealing intense staining within the caries-associated dentinal tubules. Region of higher magnification indicated by outline on the right image.