TGF-β1 secretion of ROS-17/2.8 cultures on NiTi implant material

Abstract The biocompatibility of an orthopedic implant depends on the effect of the implant on bone-forming cells, osteoblasts. Changes in osteoblastic proliferation, maturation and differentiation are important events in ossification that enable monitoring the effect of the implant. Transforming growth factor- β (TGF- β ) is known to suppress osteoblast proliferation and, on the other hand, to induce the maturation and differentiation of osteoblasts. Moreover, osteoblasts produce TGF- β , which is embedded in the bone matrix and activated by bone-resorbing osteoclasts. TGF- β inhibits osteoclastic activity. Here, we show for the first time the effect of nickel titanium shape memory metal (NiTi) on osteoblastic cytokine expression. In this study, we measured the levels of TGF- β 1 with enzyme-linked immunosorbent assay (ELISA) from a ROS-17/2.8 osteosarcoma cell line cultured on different metal alloy discs. ELISA results were proportioned to total DNA content of the samples. We compared NiTi, to stainless steel (Stst), pure titanium (Ti) and pure nickel (Ni). The TGF- β 1/DNA value in the NiTi group (0.0007±0.0003) was comparable with those seen in the Stst (0.0008±0.0001) and Ti (0.0007±0.0001) groups. The concentration in the Ni group was lower (0.0006±0.0003), though not statistically significantly so. In addition, the effect of surface roughness on TGF- β 1 production was studied. We compared three different grades of roughness in three differently hot-rolled alloys: NiTi, hot-rolled at 950°C, Ti alloy hot-rolled at 850°C (TiI) and the same Ti alloy hot-rolled at 1050°C (TiII). We found that increasing roughness of the NiTi surface increased the TGF- β 1 concentration. On the other hand, all roughness groups of TiII showed low levels of TGF- β 1, while a rough TiI surface induced similar TGF- β 1 expression as rough NiTi. Further, these same measurements made with interleukine 6 (IL-6) were found to be under the detection limit in these cultures. We conclude that a rough NiTi surface promotes TGF- β 1 expression in ROS-17/2.8 cells.