The expression of macrophage and neutrophil elastases in rat periradicular lesions.

Macrophage elastase and neutrophil elastase are involved in tissue destruction in periradicular lesions. The purpose of this study was to examine these elastases immunohistochemically during development of periradicular lesions induced in rat mandibular first molar by pulpal exposure for 7, 14, 21, 28, and 42 days. Histologically, periapical inflammation developed from 7 to 21 days and then subsided after 28 days. The area of these lesions gradually increased from 7 to 28 days and subsequently decreased at 42 days. Macrophage elastase was first detected at 7 days and predominantly shown from 14 to 28 days, whereas neutrophil elastase gradually increased from 14 to 28 days. Macrophage elastase was significantly greater than neutrophil elastase from 7 to 21 days. These results suggest that macrophage elastase was enhanced from an early stage during the development of these lesions and that neutrophil elastase was related to the expansion of periapical tissue destruction including bone resorption.