Expression analysis of matrix metalloproteinase-9 in epithelialized and nonepithelialized apical periodontitis lesions

ObjectiveThe objective of this study was to determine the expression of matrix metalloproteinase-9 (MMP-9) in apical periodontitis lesions.Study designNineteen epithelialized and 18 nonepithelialized apical periodontitis lesions were collected after periapical surgery. After histological processing, serial sectioning, H&E staining, and microscopic analysis, 10 epithelialized and 10 nonepithelialized lesions were selected for immunohistochemical analysis for MMP-9 and CD 68. At least one third of each specimen collected was frozen at –70°C for further mRNA isolation and reverse transcription into cDNA for real-time-PCR procedures. Geometric averaging of multiple housekeeping genes normalized MMP-9 mRNA expression level.ResultsPolymorphonuclear neutrophils, macrophages and lymphocytes presented MMP-9 positive immunostaining in both types of lesions. When present, epithelial cells were also stained. The number and the ratio of MMP-9+/total cells were greater in nonepithelialized than epithelialized lesions (P = .0001) presenting a positive correlation to CD68+/total cells (P = .045). Both types of lesions presented increased MMP-9 expression (P < .0001) when compared to healthy periapical ligaments. However, no significant differences were observed for MMP-9 mRNA expression between ephithelized and nonephithelized lesions.ConclusionThe present data suggest the participation of several inflammatory cells, mainly CD68+ cells, in the MMP-9 expression in apical periodontitis lesions. MMP-9 could be actively enrolled in the extracellular matrix degradation in apical periodontitis lesions.