Distribution and relative activity of matrix metalloproteinase2 in human coronal dentin

Abstract

The presence of matrix metalloproteinase2 (MMP2) in dentin has been reported, but its distribution and activity level in mature human coronal dentin are not well understood. The purpose of this study was to determine the MMP2 distribution and relative activity in demineralized dentin. Crowns of twenty eight human molars were sectioned into inner (ID), middle (MD), and outer dentin (OD) regions and demineralized. MMP2 was extracted with 0.33 molL 1 EDTA/2 molL 1 guanidineHCl, pH 7.4, and MMP2 concentration was estimated with enzymelinked immunoabsorbant assay (ELISA). Further characterization was accomplished by Western blotting analysis and gelatin zymography. The mean concentrations of MMP2 per mg dentin protein in the dentin regions were significantly different (P0.043): 0.9 ng (ID), 0.4 ng (MD), and 2.2 ng (OD), respectively. The pattern of MMP2 concentration was ODIDMD. Western blotting analysis detected 66 and 72 kDa immunopositive proteins corresponding to pro and mature MMP2, respectively, in the ID and MD, and a 66 kDa protein in the OD. Gelatinolytic activity consistent with MMP2 was detected in all regions. Interestingly, the pattern of levels of Western blot immunodetection and gelatinolytic activity was MDIDOD. The concentration of MMP2 in human coronal dentin was highest in the region of dentin that contains the dentinoenamel junction and least in the middle region of dentin. However, levels of Western blot immunodetection and gelatinolytic activity did not correlate with the estimated regional concentrations of MMP2, potentially indicating region specific protein interactions.