Effects of transforming growth factor-beta 1 (TGF-β1) on in vitro mineralization of human osteoblasts on implant materials

An in vitro cell-implant mineralization model system was used to study the effect of transforming growth factor-beta 1(TGF-β1) on mineralization in human osteoblast cultures. SaOs-2 and primary human osteoblast (HOB) cells were cultured on Tivanium (Ti–6Al–4V) disks. Administration of different concentrations of TGF-β1 (0.02, 0.01, 0.2, 1.0, 2.0 ng/ml) to these cultures demonstrated a biphasic dose response with 0.2 ng/ml TGF-β1 maximally increasing the calcium content compared to control culture. Results with SaOs-2 and HOB cultures were similar. An optimal dose of TGF-β1 (0.2 ng/ml) was provided to the cultures either in one single dose or multiple doses. Continuous administration of 0.2 ng/ml TGF-β1 caused 77% (SaOs-2) and 60% (HOB) increases in calcification compared to the control and 0.2 ng/ml single dose groups. Single administration of the accumulative dose at 1.6 ng/ml had no significant effect on the calcium content in either cell culture compared to control. Two weeks continuous administration of 0.2 ng/ml TGF-β1 in both cell cultures resulted in significant increases in the expression of bone specific extracellular matrix proteins which included alkaline phosphatase, Type I collagen, and osteocalcin as measured by Northern blot analysis and RT-PCR. At 4 weeks, the mRNA level of Type I collagen was still significantly higher in the TGF-β1 treatment group compared to control. In conclusion, TGF-β1 enhances mineralization of HOB on implant materials.