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 regulation 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 process 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 effects of TGF-beta(1) on the expression of tetranectin and alkaline phosphatase, 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 tetranectin and alkaline phosphatase expression in the early phase. Thus, TGF-beta(1) has phase-dependent effects on a human osteoblastic cell line during the process of mineralization.