Immunohistochemical expression of matrix metalloproteinase MMP-2 and MMP-9 in healthy and inflamed human dental pulp

Objective : The aim of this study was to investigate the impact of inflammation on expression of MMP-2 and MMP-9, as well as to identify the cellular sources of these enzymes in human dental pulps using immunohistochemistry. Methods : Fifty-four irreversibly inflamed samples of dental pulp were used as the experimental group. Fifty-one healthy pulps, obtained from teeth extracted for orthodontic reasons, were used as the control group. The tissue samples were formalin-fixed, paraffin-embedded, and cut into sections at 3- 4 μm. An immunohistochemical study was performed using monoclonal antibodies against MMP-2 and MMP-9. Evaluation of the immunohistochemical expression was determined by the semi-quantitative method and scored as follows: no staining (score 0), less than 10% of stained cells (score 1), less than 30% of weakly stained or strongly but incompletely stained cells (score 2), and more than 30% of strongly and completely stained cells (score 3). Results : Immunohistochemical analysis revealed a significantly greater expression of MMP-9 in inflamed than in healthy dental pulps (Mann–Whitney U, p=0.0001). In contrast, there was no difference in the expression of MMP-2 between these two groups (Mann–Whitney U, p=0.907). MMP-2 and MMP-9 immunoreactivity was detected the most frequently in endothelial cells. Conclusions : MMP-9 is highly overexpressed in inflamed dental pulps. There are no differences in the expression of MMP-2 between healthy and inflammed dental pulps. Endothelial cells represent the major cellular source of MMP-9, as well as MMP-2, in healthy and inflamed dental pulps. Keywords : dental pulp, inflammation, MMP-2, MMP-9, immunohistochemistry