Magnesium-based implants exhibit various advantages such as biodegradability and potential for enhanced in vivo bone formation. However, the cellular mechanisms behind this possible osteoconductivity remain unclear. To determine whether high local magnesium concentrations can be osteoconductive and exclude other environmental factors that occur during the degradation of magnesium implants, magnesium salt (MgCl2) was used as a model system. Because cell lines are preferred targets in studies of non-degradable implant materials, we performed a comparative study of 3 osteosarcoma-derived cell lines (MG63, SaoS2 and U2OS) with primary human osteoblasts. The correlation among cell count, viability, cell size and several MgCl2 concentrations was used to examine the influence of magnesium on proliferation in vitro. Moreover, bone metabolism alterations during proliferation were investigated by analyzing the expression of genes involved in osteogenesis. It was observed that for all cell types, the cell count decreases at concentrations above 10 mM MgCl2. However, detailed analysis showed that MgCl2 has a relevant but very diverse influence on proliferation and bone metabolism, depending on the cell type. Only for primary cells was a clear stimulating effect observed. Therefore, reliable results demonstrating the osteoconductivity of magnesium implants can only be achieved with primary osteoblasts.
Keywords: ALP, Alkaline phosphatase; BSP, Bone sialoprotein; Cbfa1, Runt-related transcription factor 2; Col, Collagen; GAPDH, Glyceraldehyde 3-phosphate dehydrogenase; HPSE, Heparanase; MG63; OB, osteoblasts; OC, Osteocalcin; OPG, Osteoprotegerin; OPN, Osteopontin; PCR, Polymerase chain reaction; RANKL, Receptor Activator of NF-κB Ligand; SaoS2; U2OS; gene expression; magnesium; osteoblasts.