The influence of biodegradable magnesium alloys on the osteogenic differentiation of human mesenchymal stem cells

The postdegradation effect of pure Mg, Mg-1Y, Mg- 5Al, and Mg-2Ca alloys on the differentiation, proliferation and gene expression of human mesenchymal stem cells (hMSCs) was investigated. It was revealed that that Mg2+ ions result in an increase in cell proliferation. However, we observed a maximum concentration (approximately 8.0 3 10-4 M) that was favourable to ATP production, above which ATP production began to decrease. In contrast to proliferation, no maximum concentration for osteogenic differentiation was observed, with increasing concentration of Mg2+ ions resulting in an increase in osteogenic differentiation across the entire tested range. Interestingly, the Mg-2Ca alloy had minimal effect on osteogenic differentiation, with Mg-1Y and pure Mg having a superior effect on the proliferation and differentiation of hMSCs. This was also observed from gene expression data, where these alloys upregulated TGFβ-1, SMAD4, FGF-2, FGF-10, and BMP-2, while SOX-2, SOX-9, and TNF-α were downregulated. Increased expression of TGFβ-1, SMAD4, BMPs, and COLIA1 protein provided further evidence to support osteogenic differentiation and that the influence of the alloying extracts on differentiation may be via the SMAD signaling pathway.