Primary osteoblasts, osteoblast precursor cells or osteoblast-like cell lines: Which human cell types are (most) suitable for characterizing 45S5-bioactive glass?

The question how bioactive glasses (BGs) influence the viability and osteogenic differentiation of human osteogenic cells has already been addressed by several studies. However, a literature review revealed great differences in the type of cells used for these experiments. Primary human osteoblasts (hOBs) represent the desired standard, but possess the limitation of patient variability and time-consuming isolation protocols. Therefore, several alternative cell types have been used including primary mesenchymal stromal cells (BMSCs) and the "osteoblast-like" cell lines MG-63, Saos-2, HOS, and U2OS. The aim of our study was the identification of the cell type most suitable for tissue engineering projects involving BGs by comparative analysis of cell viability and osteogenic differentiation in response to crystallized 45S5-BG. We observed that hOBs, BMSCs, and MG-63 cells were resistant to 45S5-BG induced cytotoxicity, while the viability of Saos-2, HOS, and U2OS cells was significantly reduced. In addition, we detected alkaline phosphatase activity, except in U2OS cells, that increased upon 45S5-BG cocultivation, demonstrating the induction of osteogenic differentiation. Our data and the fact that the donor-dependent variations can be avoided when using MG-63 cells suggest that these are a promising alternative to primary cells and remain an important cell line for future BG related studies.