Osteogenic differentiation of human mesenchymal stem cells on chargeable polymer-modified surfaces

Polystyrene cell-culture plates modified with positively charged polyallylamine (PAAm) and negatively charged poly(acrylic acid) (PAAc) and unmodified plate were used for the culture of human mesenchymal stem cells (MSCs) to study the effect of surface electrostatic properties on their osteogenic differentiation. All of these surfaces supported cell adhesion and proliferation. However, the cells adhered, spread, and proliferated somewhat more quickly on the PAAm-modified surface than they did on the PAAc-modified and control surfaces. Osteogenic differentiation was examined by alkaline phosphatase (ALP) staining, alizarin red S staining, and gene-expression analysis. The MSCs cultured on the three kinds of surfaces in the presence of dexamethasone were positively stained with ALP and alizarin red S staining, while the cells cultured without dexamethasone were not positively stained. Gene-expression analyses using real-time PCR indicated that MSCs cultured on these surfaces in the presence of dexamethasone expressed osteogenic marker genes, encoding ALP, osteocalcin, bone sialoprotein, osteopontin, and type I collagen. These results indicate that the positively charged, negatively charged, and unmodified surfaces supported osteogenic differentiation, and that their effect required the synergistic effect of dexamethasone.