Effect of cobalt and chromium ions on human MG-63 osteoblasts in vitro: Morphology, cytotoxicity, and oxidative stress

Recent studies demonstrated that Co2+ and Cr3+ ions induced cell mortality, TNF-α secretion, and oxidation of proteins in macrophages. However, little is known about the effects of corrosion products on the osteogenic cells, which have a crucial role in controlling bone remodeling. The aim of the present study was to investigate the effect of Co2+ (0–10 ppm) and Cr3+ (0–150 ppm) on human MG-63 osteoblast-like cells in term of cytotoxicity and oxidative stress. Microscopic analysis demonstrated changes in shape, size, and number of cells. Co2+ had a greater effect on these parameters than Cr3+. Cell counting showed a significant decrease in the number of MG-63 osteoblasts in a time- and dose-dependent manner, with Co2+ more toxic than Cr3+. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis also showed a decreased cellular activity in presence of Co2+ and Cr3+ ions. Oxidized and nitrated proteins, two markers of oxidative stress, were detected as single bands and revealed time- and dose-dependent protein modifications. We also studied the expression of three antioxidant enzymes. The expression of heme oxygenase-1 was increased by both ions after 24 h, before decreasing gradually thereafter. Glutathione peroxidase expression was also increased in a concentration- and time-dependent manner by both Co2+ and Cr3+ ions. Co2+ decreased catalase expression while Cr3+ increased it in a dose- and time-dependent manner. In conclusion, this study demonstrated that Cr3+ and Co2+ have a cytotoxic effect on MG-63 osteoblasts and have the potential to modify their redox state.