hibit bone resorption. Zr ions have not been assessed for osteogenic properties and it is thus possible that the benefits of incorporating Zr in implanted materials could include local direct effects on bone formation. Two forms of Zr that are readily soluble in aqueous solutions are Zirconium oxynitrate 2) and zirconium chloride and these are used in the present study to generate culture media containing Zr 
ions. The determination of the actual ionic species in aqueous solutions is complex as simple Zr4+ ions are absent in aqueous solutions where extensive hydrolysis leads to the formation of oligomeric species such as Zr448+ but for the purposes of this current study, further characterization of the actual ionic species present will not be addressed. In this study we show that Zr ions do have the ability to promote the proliferation and differentiation of human osteoblasts in vitro and that this effect is associated with, and may be mediated by, up-regulation of BMP2 expression and increased BMP signaling. Materials and Methods Isolation and culture of primary HOBs The use of primary human osteoblasts isolated from unneeded surgically removed bone was approved by the Human Ethics Committee of the University of Sydney. As the source of the bone was from minors, written informed consent was obtained from parents/guardians of the subjects. Both the protocol and the consent procedures were approved by the Human Ethics Committee of the University of Sydney. HOBs were isolated previously described from 2 / 17 Zirconium Promotes Osteoblast Differentiation discarded human vertebral trabecular bone from young healthy adolescents undergoing operations correcting scoliosis. Briefly, bone was cut into 1 mm3 pieces and washed with phosphate-buffered saline. Bone pieces were digested in 0.02% trypsin for 90 minutes at 37C. The digested cells were cultured in complete -minimal essential medium supplemented with 10% heat-inactivated fetal calf serum, 100 units/ml penicillin and streptomycin and 1 mM L-ascorbic acid phosphate magnesium salt at 37C with 5% CO2 in a humidity atmosphere. Only Passage 2 or 3 HOB cells were used PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19683642 in this study. Chemicals and HOB treatments ZrO2, ZrCl4 and sodium nitrate were purchased from Sigma-Aldrich. Zr compound solutions were PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19682619 made by dissolving the chemical powders in PBS and sterilized by filtration through 0.2 m pore syringe filters. The solutions of ZrO2 and ZrCl4 were stored at 4C as stocks at GFT505 biological activity concentrations of 5, 50 and 500 mM respectively. For use in treatment of HOB cell cultures, the stock solutions were diluted to final concentrations of Zr in the medium of 5, 50 and 500 M. HOBs were incubated in the complete medium with addition of an appropriate volume of PBS alone for untreated control conditions. An additional control containing 50 M concentration of NaNO3 in PBS was used in these studies to determine whether the NO3- ions in the ZrO 2 containing culture media may have impacted HOB osteogenesis. The medium with the treatments was refreshed every 3 days. Methylthiazolyldiphenyl-tetrazolium bromide assay HOB cells at Passage 3 were seeded in 96-well plates, 1×104 cells/well. Cells were incubated in the complete MEM containing Zr chemicals ZrO2 and ZrCl4 at different concentrations with an untreated control and a NaNO3-treated control for 1, 3 and 7 days. In each treatment group, a MTT assay was used to evaluate the number of viable cells present. HOBs were incubated with 2.5 mg/ml MTT for 2 hours at 37C. The
Comments are closed.