The messenger ion: magnesium ion coordinates bone marrow mesenchymal stem cells-mediated osteogenesis, migration, and...

Magnesium (Mg) and its alloys, as biodegradable metallic materials, possess numerous advantageous properties compared to traditional biomaterials. Furthermore, magnesium ions (Mg²⁺) are the second most abundant intracellular cations, participating in over 300 enzymatic reactions and serving as essential trace elements for various physiological processes. The release of Mg²⁺ is believed to promote osteogenic differentiation and angiogenesis, both of which are crucial for bone regeneration. However, the mechanisms underlying Mg²⁺-mediated promotion of osteogenesis and angiogenesis are not yet fully elucidated.

We treated Bone marrow mesenchymal stem cells (BMSCs) with Mg²⁺ and performed transcriptome sequencing on both control and experimental groups. Bioinformatics analysis was conducted using the sequencing data, including principal component analysis, differential expression analysis, enrichment analysis, and protein-protein interaction analysis. Pathway proteins were assessed by Western blot. The osteogenic capacity of BMSCs was directly evaluated using ALP and ARS staining. Immunofluorescence staining was used to detect the expression of osteogenesis-related proteins RUNX2 and OPN. Tube formation assays were employed to evaluate the effect of magnesium ions on angiogenesis capability, while Western blotting and quantitative PCR were used to assess changes in FGF2 and CD31 expression levels. Concurrently, the functional impact of Mg²⁺ on BMSCs was assessed using Transwell and CCK8 assays. Finally, we established a bone defect model in rats and implanted magnesium alloy scaffolds to verify the conclusions drawn from the in vitro experiments.

Through bioinformatics analysis, we identified the PI3K-AKT-mTOR pathway as a potential key pathway through which Mg²⁺ promotes osteogenesis and angiogenesis in BMSCs. Magnesium ion treatment enhanced the activity of pPI3K, pAKT, and pmTOR, elevated the expression of osteogenic and angiogenic proteins, increased ALP activity and mineralized nodule formation, and promoted tube-like structure formation. Additionally, the migratory ability, cell viability, and osteogenic activity of BMSCs were significantly elevated. Conversely, intervention with the activation of PI3K and mTOR directly affected the aforementioned outcomes, In vivo experiments also confirmed the above findings.

This study confirms that Mg²⁺ synergistically promotes osteogenic differentiation, migration of BMSCs, and angiogenesis of vascular endothelial cells by activating the PI3K-AKT-mTOR pathway. By adopting the "activation-inhibition-reversal" experimental framework and conducting in vitro and in vivo validations, the critical upstream role of PI3K and the downstream effector function of mTOR were established. These findings reveal a unified mechanism by which Mg²⁺ coordinates bone regeneration via a single signaling pathway, providing a theoretical foundation for developing smart Mg-based bone repair materials targeting this pathway.