Effect of Magnesium on Osteogenic Differentiation of Normal Human Osteoblasts

Objectives: Magnesium containing biomaterials have been increasingly used for tissue engineering and dental/orthopedic implants. However, the molecular mechanism underlying the biologic effects of magnesium is still largely unknown. In addition, the previous reports on osteogenic effect of magnesium mainly relied on the studies using ATCC osteosarcoma cell lines.
This study was designed to test the effect of magnesium on osteogenic behaviors of normal human osteoblasts.
Methods: Normal human osteoblasts derived from human alveolar bone were cultured in triplicate in growth media with varies concentrations of supplemental magnesium: 0.5mM, 1mM, 2mM, 4mM, 8mM and 16mM as the study groups and 0mM as a control group for the time intervals of 7 days, 10 days, 14 days and 21 days. Cell proliferation was measured by crystal violet dye staining. Expression of osteocalcin was measured by ELISA. Mineralization of cultures was measured by Alizarin Red staining. The data were normalized on per cell basis. Statistical analysis was done using ANOVA and Tukey HSD post-hoc tests.
Results: Osteocalcin expression was significantly up-regulated (p<0.01) in groups with supplemented magnesium at 2.0mM compared to control at all time intervals, while at supplemental magnesium concentrations of 4mM (p<0.01) and above osteocalcin expression was significantly down-regulated (p<0.01) at all time intervals. Alizarin Red stained cultures showed that mineralization was significantly enhanced (p<0.01) with 2.0mM supplement magnesium at all time intervals, while the groups with 4mM supplement magnesium and above showed lower levels of mineralization at all time intervals compared to control group.
Conclusions: Osteogenic phenotype of normal human osteoblasts including osteocalcin expression and mineralization could be significantly up-regulated by 2mM supplemental magnesium. Excessive amount of magnesium could suppress the phenotypic behavior of normal human osteoblasts. These data are important for determining ideal biomaterials with optimal concentration of magnesium for bone tissue regeneration and dental/orthopedic implants.