DETECTION OF INTERLEUKIN-1-BETA MESSENGER-RNA IN RAT PERIAPICAL LESIONS

Cells expressing interleukin-1 beta (IL-1 beta) mRNA were demonstrated by in situ hybridization in rat periapical lesions. A great number of osteoclasts with significant tartrate-resistant acid phosphatase acti vity were observed on the bone surfaces, and numerous IL-1 beta mRNA-e xpressing cells were widely distributed in the periodontal ligaments. IL-1 beta mRNA-expressing cells were mainly observed around the blood vessels in the vicinity of the bone resorption sites and occasionally found near the osteoblasts. Immunohistochemistry and enzyme histochemi stry assays showed that IL-1 beta mRNA-expressing cells were not bone cells, but that they had the characteristic features of macrophages. T hese results suggested that macrophages may contribute to the producti on of IL-1 beta and play an important role in activation of osteoclast ic bone resorption.