PHASE-DEPENDENT EFFECTS OF TRANSFORMING GROWTH-FACTOR BETA(1) ON OSTEOBLASTIC MARKERS OF HUMAN OSTEOBLASTIC CELL-LINE SV-HFO DURING MINERALIZATION

A human osteoblastic cell line (SV-HFO) established in our laboratory expresses osteoblastic markers, including mineralization in vitro, in response to differentiation-inducing agents such as dexamethasone. In this study, we examined the effects of transforming growth factor beta (1) (TGF-beta(1)) on the mineralization of SV-HFO cells and show that TGF-beta(1) inhibited the mineralization of the cells via down regulat ion of tetranectin and alkaline phosphatase without influencing other osteoblastic markers, To examine precisely the effects of TGF-beta(1) on the process of mineralization, we tentatively divided the whole pro cess of mineralization into four phases: induced ALP activity (days 0- 5), maximal ALP activity (days 5-10), early mineralization (days 10-15 ), and progressive mineralization (days 15-20). These inhibitory effec ts of TGF-beta(1) on the expression of tetranectin and alkaline phosph atase, like that on mineralization, were observed only when TGF-beta(1 ) was applied in the early phase of the process of mineralization, On the other hand, the other osteoblastic markers were not influenced by treatment with TGF-beta(1). These results suggest that TGF-beta(1) may inhibit mineralization of osteoblasts by the downregulation of tetran ectin and alkaline phosphatase expression in the early phase. Thus, TG F-beta(1) has phase-dependent effects on a human osteoblastic cell lin e during the process of mineralization.