Phase-dependent effects of transforming growth factor β1 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 β1 (TGF−β1) on the mineralization of SV-HFO cells and show that TGF−β1 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−β1 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−β1 on the expression of tetranectin and alkaline phosphatase, like that on mineralization, were observed only when TGF−β1 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−β1. These results suggest that TGF−β1 may inhibit mineralization of osteoblasts by the downregulation of tetranectin and alkaline phosphatase expression in the early phase. Thus, TGF−β1 has phase-dependent effects on a human osteoblastic cell line during the process of mineralization.