Objectives: Previous studies have reported that the expansion of dental radicular cysts is generated by the stimulation of inflammatory cytokine such as IL-1,TNF-a or PGE2. The purpose of this study was to investigate the effect of IL-1a on the expansion mechanism of dental radicular cyst. Accordingly, we determined the effect of IL-1a on an alkaline phosphatase (ALPase) activity, the mineralized nodule formation, and the expression of macrophage colony-stimulating factor (M-CSF) and osteoprotegrin (OPG) using rat osteosarcoma cell line (ROS 17/2.8). Methods: The cells were cultured with a-minimum essential medium containing 10% fetal bovine serum with or without various concentrations of IL-1a (0, 1, 10 and 100 U/ml) for up to 14 or 21 days. The mineralized nodule formation was examined by alizarin red staining, and the calcium content of mineralized nodules was determined using calcium E-test. The M-CSF expression was determined on protein level by Western blot and on mRNA level by quantitative realtime-PCR analysis. The OPG expression was determined on mRNA level by quantitative realtime-PCR analysis. Results: The ALPase activity was remarkably decreased dose-dependent of IL-1a after day 7 of culture. The mineralized nodule formation and the calcium deposits in mineralized nodules were remarkably suppressed in culture with IL-1a after day 5 of culture. The mRNA and protein expressions of M-CSF were remarkbly increased in culture with IL-1a on days 10 and 14 and on day 14 of culture, respectively. The mRNA expression of OPG was increased in culture with IL-1a on days 5 and 7 of culture, whereas the expression was not affected after day 10 of culture. Conclusions: These results indicated that IL-1a suppress osteogenesis and might convert the differentiation into osteoclasts through the increase of M-CSF produced by osteoblasts in order to expand the dental radicular cyst.

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