Effects of pseudowollastonite (CaSiO3) bioceramic on in vitro activity of human mesenchymal stem cells

We report the effects of two pseudowollastonite (β-CaSiO3) substrates on the attachment, viability, proliferation and osteogenic differentiation of human mesenchymal stem cells (hMSCs), and provide detailed mechanistic links of surface texture, soluble factors and culture media to cell activities. Cell attachment and viability were lower for psWf (fine-grained, roughness 0.74 μm) than for psWc (coarse-grained, roughness 1.25 μm) surface, and were ascribed to the greater specific area of the finer psWf particles resulting in higher release rate of Si, which is cytotoxic at high levels. Interestingly, proliferation was greater on psWf. Osteogenic differentiation occurred on both surfaces, indicated by calcium phosphate bone nodule formation and by osteocalcin, osteopontin and core-binding factor alpha-1 gene expression. Gene levels were lower on psWf than on psWc at day 8 in growth medium, explained by differences in Ca and/or Si concentrations between the two surfaces. Similar gene expression on both surfaces at day 16 in both growth and osteogenic induction media was attributed to pro-osteogenic effects of Ca and P at specific concentrations and complementary Ca and P levels on the two surfaces. In summary, soluble factors from substrates may be more important for osteogenic differentiation in growth medium than small surface roughness variations within a factor of 2. Optimum concentration ranges exist for individual soluble factors to balance cell toxicity/growth versus osteogenic differentiation, and soluble factors together have complex, cooperative or opposing, effects on a given cell activity.