Evaluating the Role of Magnesium Substitution on Osteogenic Differentiation

Objective: It is hypothesized that synthetic bone grafts can be optimized to more closely mimic the native composition and structure of mineralized tissues. Due to the presence of Mg in enamel, dentin, and bone, magnesium substituted β-tricalcium phosphate (β-TCMP) of varying Mg content was synthesized and used to study the effect of varying Mg content on the physicochemical properties and capability to promote osteogenic differentiation.

Method: X-ray diffraction and surface area measurements were conducted to characterize the material. Protein adsorption was studied using Coomassie blue staining. Cytocompatibility testing was performed using the mouse osteoblast cell line, MC3T3-E1. Cell viability and attachment were assessed using live/dead staining and the MTT assay. Cell morphology was then observed using SEM. Culture media was also collected and analyzed using ICP. qRT-PCR was performed to observe gene expression of type 1 collagen and osteocalcin.

Result: Pellets prepared with increased Mg content were observed to have greater cell attachment using live/dead staining. SEM images indicated that cells attached to pellets with greater Mg content appeared to be more spread out and well anchored, whereas cells on scaffolds prepared with less Mg content appeared to be more elongated. Despite these observed differences in attachment and morphology, cell viability, determined using the MTT assay, indicated that for all conditions viability was greater than that of cells cultured on tissue culture plastic. qRT-PCR studies revealed that cells cultured on pellets prepared with 50% Mg had a tenfold greater expression of type 1 collagen and osteocalcin compared to pure β-TCP.

Conclusion: Varying Mg content in β-TCMP greatly influences the physicochemical properties of β-TCMP and appears to promote osteogenic differentiation. By obtaining greater knowledge on the influence of Mg content on physicochemical properties, improved bone grafts can be developed. Further work using human mesenchymal stem cells (hMSCs) is currently in progress.