Effect of cobalt and chromium ions on osteoblasts in vitro

Despite the tremendous success of total hip arthroplasty (THA) in terms of cost and clinical results, this procedure has been restrained by long term outcomes. One of the major clinical concerns is the generation of UHMWPE particles leading to periprosthetic osteolysis. Because of their low volumetric wear rate, metal-on-metal bearings have emerged as an alternative. However, metal particles and ions released from metal hip prostheses due to wear and corrosion have been essential concerns for the orthopaedic community. In fact, several clinical studies have demonstrated elevated concentrations of metal ions in the systemic circulation and in the surrounding tissues in patient having a cobalt-chrome-molybdenum prosthesis. Moreover, cobalt and chromium ions are known for their potential to produce reactive oxygen species (ROS) via a Fenton-type reaction, making them prime suspects for disturbing the cellular balance of oxidants/anti-oxidants, and thus creating irreversible damage to the cell. Indeed, recent studies demonstrated that Co2+ and Cr3+ induced cell mortality and oxidation of proteins in macrophages. However, little is known about the effects of these ions 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+ and Cr 3+ ions in human MG-63 osteoblast-like cells.;In conslusion, our results suggest that Co2+ and Cr 3+ are cytotoxic, which may include creation of ROS that disturb the cellular oxidative state of MG-63 osteoblasts. The stimulation of antioxidant enzymes does not seem sufficient to prevent cell death.;Our studies demonstrated that Co2+ and Cr3+ ions decreased the number of living cells and reduced the cellular activity of MG-63 osteoblasts. Likewise, microscopic observations revealed clear changes in terms of shape, size, and number of cells. Furthermore, Co2+ seems more toxic than Cr3+. Western blot analysis showed the induction of protein oxidation and protein nitration, which are biomarkers of oxidative stress, in a dose- and time-dependent manner with both ions. Antioxidant enzymes were also affected by the presence of ions, but in varying ways. HO-1 expression reached 6.0 and 1.9 times the control after 24h with 10 ppm Co2+ and 150 ppm Cr3+, respectively before decreasing thereafter. GPx expression was increased in a concentration- and time-dependent manner by Co2+ and Cr3+. CAT expression was decreased in the presence of Co2+ and up-reguated with Cr3+.