Differentiation of human mesenchymal stem cells on nano- and micro-grain size titania

The current study investigated the osteogenic differentiation of human mesenchymal stem cells cultured on titania surfaces with grain sizes ranging from 50 to 1500 nm in either control or osteogenic medium. Characterization of osteogenic differentiation included quantification of the osteopontin and alkaline phosphatase expression by the cells, as well as of the content of calcium in the extracellular matrix. Mesenchymal stem cell differentiation was not observed on any of the grain sizes tested without dexamethasone and osteogenic-stimulating chemical agents (specifically, ascorbic acid and beta-glycerolphosphate) in the culture medium. Little-to-no mesenchymal stem cell differentiation was detected on the 50 nm substrates under osteogenic media. In contrast, osteogenic differentiation occurred earlier, and to greater extent, on the 200 nm grain size titania, compared to results obtained on either the 50 or 1500 nm grain sizes, or the glass (reference) surfaces, under osteogenic media. These results demonstrated that biomaterial substrate topography, such as ceramic grain size, affects mesenchymal stem cell differentiation in a size-dependent but, non-linear, manner.