Magnesium Ions Promote the Biological Behaviour of Rat Calvarial Osteoblasts by Activating the PI3K/Akt Signalling Pathway

Magnesium has been investigated as a biodegradable metallic material. Increased concentrations of Mg²⁺ around magnesium implants due to biodegradation contribute to its satisfactory osteogenic capacity. However, the mechanisms underlying this process remain elusive. We propose that activation of the PI3K/Akt signalling pathway plays a role in the Mg²⁺-enhanced biological behaviours of osteoblasts. To test this hypothesis, 6, 10 and 18 mM Mg²⁺ was used to evaluate the stimulatory effect of Mg²⁺ on osteogenesis, which was assessed by evaluating cell adhesion, cell viability, ALP activity, extracellular matrix mineralisation and RT-PCR. The expression of p-Akt was also determined by western blotting. The results showed that 6 and 10 mM Mg²⁺ elicited the highest stimulatory effect on cell adhesion, cell viability and osteogenic differentiation as evidenced by cytoskeletal staining, MTT assay results, ALP activity, extracellular matrix mineralisation and expression of osteogenic differentiation-related genes. In contrast, 18 mM Mg²⁺ had an inhibitory effect on the behaviour of osteoblasts. Furthermore, 10 mM Mg²⁺ significantly increased the phosphorylation of Akt in osteoblasts. Notably, the aforementioned beneficial effects produced by 10 mM Mg²⁺ were abolished by blocking the PI3K/Akt signalling pathway through the addition of wortmannin. In conclusion, these results demonstrate that 6 mM and 10 mM Mg²⁺ can enhance the behaviour of osteoblasts, which is at least partially attributed to activation of the PI3K/Akt signalling pathway. Furthermore, a high concentration (18 mM Mg²⁺) showed an inhibitory effect on the biological behaviour of osteoblasts. These findings advance the understanding of cellular responses to biodegradable metallic materials and may attract greater clinical interest in magnesium.