Localization of IL-1α, IL-1 RI, TNF, TNF-RI and TNF-RII during physiological drift of rat molar teeth -: An immunohistochemical and in situ hybridization study

Proinflammatory cytokines such as IL-1 and TNF play a crucial role in the initiation of an inflammatory response to bacterial irritants and subsequent periodontal tissue destruction. The object of the present investigation was to examine the possible role of these cytokines in the periodontal tissues under physiological conditions. To this end we studied the expression of IL-1alpha and TNF both at the transcription and protein level by means of in situ hybridization and immunohistochemistry and investigated the distribution of IL-1RI, TNF-RI and TNF-RII immunohistochemically in 10 jaw specimens taken from male Wistar rats. We found IL-1alpha and TNF mRNA to be focally transcribed in bone marrow cells of the monocyte/macrophage lineage, in gingival epithelium as well as in single osteoblasts and osteoclasts. Additionally, IL-1alpha mRNA was detected in PDL-fibroblasts and epithelial remnants of Malassez. The IL-1alpha immunohistochemistry observations were corroborated by the in situ hybridization results. TNF and its receptors were not detected at the protein level. These data suggest that IL-1alpha, and its receptor are of some importance in the maintenance of tissue homeostasis and remodeling events accompanied by physiological tooth movement. (C) 2002 Elsevier Science Ltd. All rights reserved.