EFFECTS OF SEVERAL CYTOKINES ON THE FUNCTIONS OF FETAL RAT OSTEOBLAST-LIKE CELLS IN VITRO

Effects of several cytokines($IL-1{\beta},\;TNF_{\alpha},\;and\;IFN_{\gamma}$) have been examined on fetal rat osteoblast-like cells. To investigate whether cytokines play direct causal roles in production of lysosomal enzyme, fetal rat osteoblast-like cells were treated with $IL-1{\beta},\;TNF_{\alpha},\;and\;IFN_{\gamma}$, respectively or combined. And acid phosphatase was determined by biochemical method. Alkaline phosphatase was assayed to determine the effects of $IL-1{\beta},\;TNF_{\alpha},\;and\;IFN_{\gamma}$ on the expression of this enzyme. And also experiment of calcified nodule formation was performed to assess the effects of cytokines on the bone-forming activity of osteoblast-like cells in vitro. Acid phosphatase activity was significantly increased by the addition of $IL-1{\beta}\;and\;TNF_{\alpha}$, whereas decreased by $IFN_{\gamma}$. However, no significant change:: in alkaline phosphatase activity was observed when the osteoblast-like cells were treated with $IL-1{\beta}\;and\;TNF_{\alpha}$. Interestingly, $IFN_{\gamma}$ showed stimulatory effect on alkaline phosphatase activity. The number of calcified nodules was decreased by treatment of cultures with 1 ng/ml $IL-1{\beta},\;20\;ng/ml\;TNF_{\alpha}$, and 500 u/ml $IFN_{\gamma}$ continuously for 21 days, while considerable number of calcified nodules were formed in control group of osteoblast-like cell in culture for 21 days. These results seem to suggest that cytokines may play crucial roles in bone remodeling through the direct action on the osteoblast-like cell.