Histochemical localization of neutral proteases released during development of rat periradicular lesion.

OBJECTIVE: The purpose of the present study was to examine the role of various neutral proteases released during the development of periradicular lesion. DESIGN: This lesion produced by pulpal exposure of mandibular first molar in rat. The histological and histometrical changes in periapical tissue examined. The presence of neutrophil elastase, cathepsin G, collagenase 2, gelatinase B, and secretory leukocyte protease inhibitor (SLPI) was immunohistochemically evaluated in the periapical tissue. RESULTS: After pulpal exposure, some inflammatory cells were present in the periapical tissue at 7 days, and periapical inflammation gradually increased. Alveolar bone resorption observed after 14 days and apical abscess found after 21 days. After 14 days, the area of periradicular lesion significantly increased compared from normal one (p<0.05). Neutrophil elastase, cathepsin G, collagenase 2, and gelatinase B were detected around the root apex at 14 days, then these proteases increased gradually and demonstrated in and around the abscess at 21 and 28 days. Morphologically, these protease-expressing cells are almost polymorphic and polynuclear shaped after 14 days. These cells significantly increased after 14 days compared from normal one (p<0.05). However, SLPI detected after 21 days around apical root. It significantly increased after 21 days (p<0.05). CONCLUSIONS: These results suggested that neutrophil elastase, cathepsin G, collagenase 2, and gelatinase B induce the destruction of periapical tissue. We demonstrated that these neutral proteases released play an important role in development of periradicular lesion.

Matrix metalloproteinase-3 accelerates wound healing following dental pulp injury.

Matrix metalloproteinases (MMPs) are implicated in a wide range of physiological and pathological processes, including morphogenesis, wound healing, angiogenesis, inflammation, and cancer. Angiogenesis is essential for reparative dentin formation during pulp wound healing. The mechanism of angiogenesis, however, still remains unclear. We hypothesized that certain MMPs expressed during pulp wound healing may support recovery processes. To address this issue, a rat pulp injury model was established to investigate expression of MMPs during wound healing. Real-time RT-PCR analysis showed that expression MMP-3 and MMP-9 (albeit lower extent) was up-regulated at 24 and 12 hours after pulp injury, respectively, whereas expression of MMP-2 and MMP-14 was not changed. MMP-3 mRNA and protein were localized in endothelial cells and/or endothelial progenitor cells in injured pulp in vivo. In addition, MMP-3 enhanced proliferation, migration, and survival of human umbilical vein endothelial cells in vitro. Furthermore, the topical application of MMP-3 protein on the rat-injured pulp tissue in vivo induced angiogenesis and reparative dentin formation at significantly higher levels compared with controls at 24 and 72 hours after treatment, respectively. Inhibition of endogenous MMP-3 by N-Isobutyl-N-(4-methoxyphenylsulfonyl)-glycylhydroxamic acid resulted in untoward wound healing. These results provide suggestive evidence that MMP-3 released from endothelial cells and/or endothelial progenitor cells in injured pulp plays critical roles in angiogenesis and pulp wound healing.