Effect of magnesium ion on human osteoblast activity

Abstract

Magnesium, a promising biodegradable metal, has been reported in several studies to increase bone formation. Although there is some information regarding the concentrations of magnesium ions that affect bone remodeling at a cellular level, little is known about the effect of magnesium ions on cell gap junctions. Therefore, this study aimed to systematically investigate the effects of different concentrations of magnesium on bone cells, and further evaluate its effect on gap junctions of osteoblasts. Cultures of normal human osteoblasts were treated with magnesium ions at concentrations of 1, 2 and 3 mM, for 24, 48 and 72 h. The effects of magnesium ions on viability and function of normal human osteoblasts and on gap junction intercellular communication (GJIC) in osteoblasts were investigated. Magnesium ions induced significant (P<0.05) increases in cell viability, alkaline phosphate activity and osteocalcin levels of human osteoblasts. These stimulatory actions were positively associated with the concentration of magnesium and the time of exposure. Furthermore, the GJIC of osteoblasts was significantly promoted by magnesium ions. In conclusion, this study demonstrated that magnesium ions induced the activity of osteoblasts by enhancing GJIC between cells, and influenced bone formation. These findings may contribute to a better understanding of the influence of magnesium on bone remodeling and to the advance of its application in clinical practice.

Figure 1. Average absorbance of osteoblasts treated with magnesium (Mg²⁺). The absorbance of cells increased with the increasing concentration of Mg²⁺ and with longer exposure time. ^@,+,&P<0.05, differences over time at concentrations of 1, 2 and 3 mM, respectively. ^#P<0.05, differences among various concentrations of magnesium at each time point; *P<0.05, differences from the control group at each time point (ANOVA).

Figure 2. Average alkaline phosphatase (ALP) activity for osteoblastic cells treated with magnesium (Mg²⁺). The level of ALP activity for osteoblasts was stimulated by (Mg²⁺), and was positively associated with the concentration of Mg²⁺ and the time of exposure. ^@,+,&P<0.05, differences over time at concentrations of 1, 2 and 3 mM, respectively. ^#P<0.05, differences among various concentrations of Mg²⁺ at each time point. *P<0.05, differences from the control group at each time point (ANOVA).

Figure 3. Average osteocalcin levels in osteoblasts treated with magnesium (Mg²⁺). The stimulation action of Mg²⁺ was positively associated with concentrations of Mg²⁺ and time of exposure. ^@,+,&P<0.05, for differences over time at concentrations of 1, 2 and 3 mM, respectively. ^#P<0.05, for differences among various concentrations of Mg²⁺ at each time point. *P<0.05, for differences from the control group at each time point (ANOVA).

Figure 4. Average fluorescence recovery (R value) for osteoblasts treated with magnesium (Mg²⁺). The stimulation action was positively associated with the concentration of Mg²⁺ and the time of exposure. ^@,+,&P<0.05, for differences over time at concentrations of 1, 2 and 3 mM, respectively. ^#P<0.05, for differences among various concentrations of Mg²⁺ at each time point. *P<0.05, for differences from the control group at each time point (ANOVA).