Development of a new culture model for the screening of a agent to increase the bone formation

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Effects of Growth factors on the bone nodule formation in osteoblasts from aged rats.1.We found that the basic fibroblast growth factor (bFGF) is potent to increase the bone nodule formation, when added to the culture medium, in the short period of the growth phase of osteoblasts.2.The Fffect to increase the bone nodule formation is maximal at 5ng/ml. This effect is more remarkable in osteoblasts from fetal rats (FOB) than those of aged rats (AOB).3.When other growth factors, such as aFGF,FGF,IGF-I,IGF-II,PDGF,TGF-beta, was added to the culture medium, bFGF,aFGF,IGF-I,IGF-II,PDGF,and TGF-beta increased the cell division, but only BFGF and PDGF enhances the bone nodule formation in FOB.In the case of AOB,the effect on the cell division was similar to the results of FOB,but only bFGF enhanced the bone nodule formation.Effects of Dexamethasone on the bone nodule formation in osteoblasts from aged rats.After the extensive screening of the other growth factors and hormones, we found that dexamethasone remarkably recovered the bone nodule formation activity in the osteoblasts from aged rats, when added simultaneously with bFGF.Dexamethasone and bFGF also increased the alkaline phosphatase activity in the course of bone nodule formation. In other hand, dexamethasone only slightly increased the bone nodule formation and alkaline phosphatase in FOB,when added simultaneously with bFGF.This was because of the results that bFGF itself has strong effects to increase the bone nodule formation in FOB.In the case of osteoblast-like cell line, such as ROS 17/2.8, MC3T3-E1 and UMR106, synergistic effect of dexamethasone and bFGF to increase the alkaline phosphatase activity was not observed.From the result described above, we suggests that there is a distinct species of osteoblast which is able to respond to bFGF and dexamethasone in AOB.This in vitro culture experimental model will be useful to investigate the mechanism of the bone formation in aged animals.